Split Stereo Display (non head-mounted) [Custom Resolution?]

Can we render a "split stereo" texture to a RenderTexture?
This is in fact rendering to a RenderTargetView in D3D11.

I want to be able to control the split view resolution. How would I do this?
"UnityEngine.VR.VRSettings.renderScale" is not good enough as I cant set the texture aspect.

The goal here is to get a optimized stereo rendered scene in the form of a D3D11 RenderTargetView for a native plugin. Probably getting access via a RenderTexture object.