diff --git a/src/assets.rs b/src/assets.rs
deleted file mode 100644
index 36a59b6..0000000
--- a/src/assets.rs
+++ /dev/null
@@ -1,43 +0,0 @@
-use bevy::prelude::*;
-use bevy_common_assets::ron::RonAssetPlugin;
-use serde::Deserialize;
-
-use crate::{
-    simulator::{balloon::BalloonMaterial, gas::GasSpecies},
-    AppState,
-};
-
-/// Configuration for the properties of gases and materials.
-#[derive(Asset, Debug, Deserialize, TypePath)]
-pub struct PropertiesConfig {
-    pub gases: Vec<GasSpecies>,
-    pub materials: Vec<BalloonMaterial>,
-}
-
-impl Default for PropertiesConfig {
-    fn default() -> Self {
-        Self { gases: vec![], materials: vec![] }
-    }
-}
-
-/// Plugin for loading configuration.
-pub struct ConfigLoaderPlugin;
-
-impl Plugin for ConfigLoaderPlugin {
-    fn build(&self, app: &mut App) {
-        app.add_plugins(RonAssetPlugin::<PropertiesConfig>::new(&["ron"]))
-            .insert_resource(PropertiesConfig::default())
-            .add_systems(
-                Startup,
-                load_configs,
-            );
-    }
-}
-
-/// Loads the configuration and transitions to the Running state.
-fn load_configs(asset_server: Res<AssetServer>, mut commands: Commands) {
-    info!("Setting up configuration loader");
-    let handle = asset_server.load("configs/properties.ron");
-    commands.insert_resource(handle.clone());
-    info!("Configuration loader setup complete");
-}
diff --git a/src/lib.rs b/src/lib.rs
index 1000bcb..80f997b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,9 +2,6 @@ mod app3d;
 mod controls;
 mod simulator;
 
-#[cfg(feature = "config-files")]
-mod assets;
-
 use bevy::{asset::AssetMetaCheck, prelude::*};
 
 pub struct YahsPlugin;
diff --git a/src/simulator/properties.rs b/src/simulator/properties.rs
index 038e26d..4117843 100644
--- a/src/simulator/properties.rs
+++ b/src/simulator/properties.rs
@@ -4,10 +4,13 @@
 
 use std::ops::{Add, Div, Mul, Sub};
 
-use avian3d::{math::{Scalar, PI}, prelude::{ColliderDensity, ColliderMassProperties, PhysicsSet, RigidBody}};
+use avian3d::{
+    math::{Scalar, PI},
+    prelude::{ColliderDensity, ColliderMassProperties, PhysicsSet, RigidBody},
+};
 use bevy::{prelude::*, reflect::Reflect};
 #[cfg(feature = "config-files")]
-use serde::{Serialize, Deserialize};
+use serde::{Deserialize, Serialize};
 
 pub const BOLTZMANN_CONSTANT: f32 = 1.38e-23_f32; // [J/K]
 pub const AVOGADRO_CONSTANT: f32 = 6.022e+23_f32; // [1/mol]
@@ -45,9 +48,14 @@ impl Plugin for CorePropertiesPlugin {
         app.register_type::<Mass>();
         app.register_type::<MolarMass>();
 
-        // Ensure that the Avian density matches our computed density before
-        // solving physics.
-        app.add_systems(Update, sync_avian_density.in_set(PhysicsSet::Prepare));
+        // Ensure that the Avian density matches our computed mass and density
+        // before it starts solving physics.
+        app.add_systems(
+            Update,
+            (sync_avian_mass, sync_avian_density)
+                .chain()
+                .in_set(PhysicsSet::Prepare),
+        );
     }
 }
 
@@ -268,7 +276,7 @@ impl Div<Scalar> for Density {
     }
 }
 
-fn sync_avian_density(mut densities: Query<(&mut ColliderDensity, &Volume, &Mass), With<RigidBody>>) {
+fn sync_avian_density(mut densities: Query<(&mut ColliderDensity, &Volume, &Mass)>) {
     for (mut density, volume, mass) in densities.iter_mut() {
         let our_density = mass.kg() / volume.m3();
         density.0 = our_density;
@@ -334,6 +342,12 @@ impl Div<Scalar> for Mass {
     }
 }
 
+fn sync_avian_mass(mut bodies: Query<(&mut ColliderMassProperties, &Mass)>) {
+    for (mut mass_props, mass) in bodies.iter_mut() {
+        mass_props.mass.0 = mass.0;
+    }
+}
+
 /// Molar mass (kg/mol) of a substance.
 #[derive(Component, Debug, Default, Clone, Copy, PartialEq, Reflect)]
 #[cfg_attr(feature = "config-files", derive(Serialize, Deserialize))]