Forward rendering performance drop for VR

Forward shading config settings as follows:

r.DefaultFeature.AntiAliasing=3
r.EarlyZPass=2
r.EarlyZPassMovable=True
r.DBuffer=True
r.ForwardShading=True
vr.InstancedStereo=True

Scene is a typical outdoor scene with a Skylight sky and directional “sun” light. After turning on forward rendering render time went from 6.55ms (deferred) to 11.05ms (forward). I have attached the reference scenes (left is deferred) and the GPU profiles. The biggest leap seems to be in computing shadows… which I was not aware would be affected by switching to the forward renderer.

Been poking around with it a bit more. Still haven’t determined the performance loss.