ScreenSpace Canvas in VR on Oculus

I'm building a targetbox system for a vr game, and I ran into issues with worldToScreenPoint.
When I'm running the following code with the headset unplugged, it runs fine, but with the headset plugged, its a bit ambiguous which screen it is getting values from.
The width and height of the target boxes from this function are roughly correct, but the position is incorrect

Code (CSharp):

1.  
2.           public static Rect GetScreenRect(Bounds bounds, Camera cam)
3.         {
4.             // Sourced from: https://answers.unity.com/questions/49943
5.             // optimized!
6.            
7.             Vector3 ext = bounds.extents;
8.             Vector3 cen = bounds.center;
9.  
10.             Vector2 min = cam.WorldToScreenPoint(new Vector3(cen.x - ext.x, cen.y - ext.y, cen.z - ext.z));
11.             Vector2 max = min;
12.  
13.             //0
14.             Vector2 point = min;
15.             get_minMax(point, ref min, ref max);
16.  
17.             //1
18.             point = cam.WorldToScreenPoint(new Vector3(cen.x + ext.x, cen.y - ext.y, cen.z - ext.z));
19.             get_minMax(point, ref min, ref max);
20.  
21.  
22.             //2
23.             point = cam.WorldToScreenPoint(new Vector3(cen.x - ext.x, cen.y - ext.y, cen.z + ext.z));
24.             get_minMax(point, ref min, ref max);
25.  
26.             //3
27.             point = cam.WorldToScreenPoint(new Vector3(cen.x + ext.x, cen.y - ext.y, cen.z + ext.z));
28.             get_minMax(point, ref min, ref max);
29.  
30.             //4
31.             point = cam.WorldToScreenPoint(new Vector3(cen.x - ext.x, cen.y + ext.y, cen.z - ext.z));
32.             get_minMax(point, ref min, ref max);
33.  
34.             //5
35.             point = cam.WorldToScreenPoint(new Vector3(cen.x + ext.x, cen.y + ext.y, cen.z - ext.z));
36.             get_minMax(point, ref min, ref max);
37.  
38.             //6
39.             point = cam.WorldToScreenPoint(new Vector3(cen.x - ext.x, cen.y + ext.y, cen.z + ext.z));
40.             get_minMax(point, ref min, ref max);
41.  
42.             //7
43.             point = cam.WorldToScreenPoint(new Vector3(cen.x + ext.x, cen.y + ext.y, cen.z + ext.z));
44.             get_minMax(point, ref min, ref max);
45.  
46.             return new Rect(min.x, min.y, max.x - min.x, max.y - min.y);
47.         }
48.  
49.  
50.  
51.         [MethodImpl(MethodImplOptions.AggressiveInlining)]
52.         static void get_minMax(Vector2 point, ref Vector2 min, ref Vector2 max)
53.         {
54.             min = new Vector2(min.x >= point.x ? point.x : min.x, min.y >= point.y ? point.y : min.y);
55.             max = new Vector2(max.x <= point.x ? point.x : max.x, max.y <= point.y ? point.y : max.y);
56.         }