Stereoscopic Occlusion Culling?

Does anyone have any bright ideas on how to work with Occlusion Culling systems and stereo cameras? screenshot should demonstrate the issue pretty easily. this might be a pretty large problem for me/architecture in general, as the scale of the projects don't lend themselves very well to just frustum culling quite often!

Screenshot taken using the occlusion culling window and automatic portal generation.



The issue comes up in several built in unity systems however, the terrain system + tree's being the other REALLY blatantly wrong case.