Made Callbacks into a property and just use rounding to int for dealing with floating point inaccuracies.

Assets/Scripts/Core/Fsr2.cs

@@ -83,8 +83,8 @@ namespace FidelityFX
             int displayWidth, int displayHeight, QualityMode qualityMode)
         {
             float ratio = GetUpscaleRatioFromQualityMode(qualityMode);
-            renderWidth = (int)(displayWidth / ratio + 0.01f);
-            renderHeight = (int)(displayHeight / ratio + 0.01f);
+            renderWidth = Mathf.RoundToInt(displayWidth / ratio);
+            renderHeight = Mathf.RoundToInt(displayHeight / ratio);
         }
         
         public static float GetMipmapBiasOffset(int renderWidth, int displayWidth)

Assets/Scripts/Fsr2ImageEffect.cs

@@ -34,7 +34,7 @@ namespace FidelityFX
     [RequireComponent(typeof(Camera))]
     public class Fsr2ImageEffect : MonoBehaviour
     {
-        public IFsr2Callbacks Callbacks = new Fsr2CallbacksBase();
+        public IFsr2Callbacks Callbacks { get; set; } = new Fsr2CallbacksBase();
         
         public Fsr2.QualityMode qualityMode = Fsr2.QualityMode.Quality;