diff --git a/frc971/control_loops/drivetrain/drivetrain_config.h b/frc971/control_loops/drivetrain/drivetrain_config.h
index 9150e8a..51f92b1 100644
--- a/frc971/control_loops/drivetrain/drivetrain_config.h
+++ b/frc971/control_loops/drivetrain/drivetrain_config.h
@@ -49,6 +49,31 @@
   int do_accel_corrections = 50;
 };
 
+// Configuration for line-following mode.
+struct LineFollowConfig {
+  // The line-following uses an LQR controller with states of [theta,
+  // linear_velocity, angular_velocity] and inputs of [left_voltage,
+  // right_voltage].
+  // These Q and R matrices are the costs for state and input respectively.
+  Eigen::Matrix3d Q =
+      Eigen::Matrix3d((::Eigen::DiagonalMatrix<double, 3>().diagonal()
+                           << 1.0 / ::std::pow(0.1, 2),
+                       1.0 / ::std::pow(1.0, 2), 1.0 / ::std::pow(1.0, 2))
+                          .finished()
+                          .asDiagonal());
+  Eigen::Matrix2d R =
+      Eigen::Matrix2d((::Eigen::DiagonalMatrix<double, 2>().diagonal()
+                           << 1.0 / ::std::pow(12.0, 2),
+                       1.0 / ::std::pow(12.0, 2))
+                          .finished()
+                          .asDiagonal());
+
+  // The driver can use their steering controller to adjust where we attempt to
+  // place things laterally. This specifies how much range on either side of
+  // zero we allow them, in meters.
+  double max_controllable_offset = 0.1;
+};
+
 template <typename Scalar = double>
 struct DrivetrainConfig {
   // Shifting method we are using.
@@ -118,6 +143,8 @@
 
   DownEstimatorConfig down_estimator_config{};
 
+  LineFollowConfig line_follow_config{};
+
   // Converts the robot state to a linear distance position, velocity.
   static Eigen::Matrix<Scalar, 2, 1> LeftRightToLinear(
       const Eigen::Matrix<Scalar, 7, 1> &left_right) {
diff --git a/frc971/control_loops/drivetrain/line_follow_drivetrain.cc b/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
index a53538b..95f14a3 100644
--- a/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
+++ b/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
@@ -95,6 +95,8 @@
     const DrivetrainConfig<double> &dt_config,
     TargetSelectorInterface *target_selector)
     : dt_config_(dt_config),
+      Q_(dt_config_.line_follow_config.Q),
+      R_(dt_config_.line_follow_config.R),
       A_d_(ADiscrete(dt_config_)),
       B_d_(BDiscrete(dt_config_)),
       K_(CalcK(A_d_, B_d_, Q_, R_)),
@@ -131,7 +133,8 @@
   }
   // Set an adjustment that lets the driver tweak the offset for where we place
   // the target left/right.
-  side_adjust_ = -goal->wheel() * 0.1;
+  side_adjust_ =
+      -goal->wheel() * dt_config_.line_follow_config.max_controllable_offset;
 }
 
 bool LineFollowDrivetrain::SetOutput(
diff --git a/frc971/control_loops/drivetrain/line_follow_drivetrain.h b/frc971/control_loops/drivetrain/line_follow_drivetrain.h
index 24f8cd4..c5b03f0 100644
--- a/frc971/control_loops/drivetrain/line_follow_drivetrain.h
+++ b/frc971/control_loops/drivetrain/line_follow_drivetrain.h
@@ -1,7 +1,6 @@
 #ifndef FRC971_CONTROL_LOOPS_DRIVETRAIN_LINE_FOLLOW_DRIVETRAIN_H_
 #define FRC971_CONTROL_LOOPS_DRIVETRAIN_LINE_FOLLOW_DRIVETRAIN_H_
 #include "Eigen/Dense"
-
 #include "frc971/control_loops/control_loops_generated.h"
 #include "frc971/control_loops/drivetrain/drivetrain_config.h"
 #include "frc971/control_loops/drivetrain/drivetrain_goal_generated.h"
@@ -56,21 +55,10 @@
                    double relative_y_offset, double velocity_sign);
 
   const DrivetrainConfig<double> dt_config_;
-  // TODO(james): These should probably be factored out somewhere.
   // TODO(james): This controller is not actually asymptotically stable, due to
   // the varying goal theta.
-  const ::Eigen::DiagonalMatrix<double, 3> Q_ =
-      (::Eigen::DiagonalMatrix<double, 3>().diagonal()
-           << 1.0 / ::std::pow(0.1, 2),
-       1.0 / ::std::pow(1.0, 2), 1.0 / ::std::pow(1.0, 2))
-          .finished()
-          .asDiagonal();
-  const ::Eigen::DiagonalMatrix<double, 2> R_ =
-      (::Eigen::DiagonalMatrix<double, 2>().diagonal()
-           << 1.0 / ::std::pow(12.0, 2),
-       1.0 / ::std::pow(12.0, 2))
-          .finished()
-          .asDiagonal();
+  const ::Eigen::Matrix<double, 3, 3> Q_;
+  const ::Eigen::Matrix<double, 2, 2> R_;
   // The matrices we use for the linear controller.
   // State for these is [theta, linear_velocity, angular_velocity]
   const ::Eigen::Matrix<double, 3, 3> A_d_;
diff --git a/frc971/control_loops/drivetrain/localization/puppet_localizer.cc b/frc971/control_loops/drivetrain/localization/puppet_localizer.cc
index 3125793..33095f2 100644
--- a/frc971/control_loops/drivetrain/localization/puppet_localizer.cc
+++ b/frc971/control_loops/drivetrain/localization/puppet_localizer.cc
@@ -7,7 +7,9 @@
 PuppetLocalizer::PuppetLocalizer(
     aos::EventLoop *event_loop,
     const frc971::control_loops::drivetrain::DrivetrainConfig<double>
-        &dt_config)
+        &dt_config,
+    std::unique_ptr<frc971::control_loops::drivetrain::TargetSelectorInterface>
+        target_selector)
     : event_loop_(event_loop),
       dt_config_(dt_config),
       ekf_(dt_config),
@@ -17,7 +19,8 @@
               "/localizer")),
       clock_offset_fetcher_(
           event_loop_->MakeFetcher<aos::message_bridge::ServerStatistics>(
-              "/aos")) {
+              "/aos")),
+      target_selector_(std::move(target_selector)) {
   ekf_.set_ignore_accel(true);
 
   event_loop->OnRun([this, event_loop]() {
@@ -25,7 +28,11 @@
                            HybridEkf::State::Zero(), ekf_.P());
   });
 
-  target_selector_.set_has_target(false);
+  if (!target_selector_) {
+    auto selector = std::make_unique<TrivialTargetSelector>();
+    selector->set_has_target(false);
+    target_selector_ = std::move(selector);
+  }
 }
 
 void PuppetLocalizer::Reset(
diff --git a/frc971/control_loops/drivetrain/localization/puppet_localizer.h b/frc971/control_loops/drivetrain/localization/puppet_localizer.h
index 4f8f4f3..24e2f88 100644
--- a/frc971/control_loops/drivetrain/localization/puppet_localizer.h
+++ b/frc971/control_loops/drivetrain/localization/puppet_localizer.h
@@ -32,14 +32,17 @@
   PuppetLocalizer(
       aos::EventLoop *event_loop,
       const frc971::control_loops::drivetrain::DrivetrainConfig<double>
-          &dt_config);
+          &dt_config,
+      std::unique_ptr<
+          frc971::control_loops::drivetrain::TargetSelectorInterface>
+          target_selector = {});
   frc971::control_loops::drivetrain::HybridEkf<double>::State Xhat()
       const override {
     return ekf_.X_hat().cast<double>();
   }
-  frc971::control_loops::drivetrain::TrivialTargetSelector *target_selector()
+  frc971::control_loops::drivetrain::TargetSelectorInterface *target_selector()
       override {
-    return &target_selector_;
+    return target_selector_.get();
   }
 
   void Update(const ::Eigen::Matrix<double, 2, 1> &U,
@@ -97,7 +100,8 @@
   aos::Fetcher<aos::message_bridge::ServerStatistics> clock_offset_fetcher_;
 
   // Target selector to allow us to satisfy the LocalizerInterface requirements.
-  frc971::control_loops::drivetrain::TrivialTargetSelector target_selector_;
+  std::unique_ptr<frc971::control_loops::drivetrain::TargetSelectorInterface>
+      target_selector_;
 };
 
 }  // namespace drivetrain
diff --git a/frc971/control_loops/drivetrain/localizer.h b/frc971/control_loops/drivetrain/localizer.h
index 67d681e..d590f1d 100644
--- a/frc971/control_loops/drivetrain/localizer.h
+++ b/frc971/control_loops/drivetrain/localizer.h
@@ -15,6 +15,7 @@
 // state updates and then determine what poes we should be driving to.
 class TargetSelectorInterface {
  public:
+  virtual ~TargetSelectorInterface() {}
   // Take the state as [x, y, theta, left_vel, right_vel]
   // If unable to determine what target to go for, returns false. If a viable
   // target is selected, then returns true and sets target_pose.
@@ -108,6 +109,7 @@
 // manually set the target selector state.
 class TrivialTargetSelector : public TargetSelectorInterface {
  public:
+  virtual ~TrivialTargetSelector() {}
   bool UpdateSelection(const ::Eigen::Matrix<double, 5, 1> &, double) override {
     return has_target_;
   }