Render Target in Post Process Material for VR

So I am trying to make a method of switching cameras with a transition effect. Basically, the new view starts as a box in the center and expands, filling the screen. The way I more or less figured out how to do this was to create the mask in a post process material, and feed the mask into a lerp, with A being a SceneTexture:PostProcessInput0, and B being a render target from the destination camera. Then when it wipes, teleport the actor and switch back to PostProcessInput0. Of course its not perfect since PostProcessInput0 doesn’t take into effect all visual effects, but it works well enough.
The issue I am having however, is when I am putting the Render Target onto the camera, because it is in VR, the eyes view it differently, so you don’t get the clean stereoscopic effect. I have been looking at different sources such as

or other sources talking about using an if statement to render differently in different eyes, but so far I am having no success.

Any suggestions on how to fix this? Or any methods that may be better for grabbing the input of 2 cameras and doing a mask transition between them?