Let me add this image to show you what I mean.
It's a partial screen grab of a UltraHigh build spot, which is
1. well inside of the bounding box,
2. has no masks to prevent the area from being generated
3. builds fine when doing a full high build
and, since this cut off line is so obvious(white area is the actual surface, dark area is the opposite side, not facing the camera), I make an assumption that Photoscan discards a few photos, which are actually needed to get this area built.
I wish I could build this whole thing at ultra high, so it would reconstruct everything, but I cannot due to my 24gig RAM limit. But, even then, this makes me wonder if there are other spots which PS could potentially do a better job at building, but doesn't due to the insufficient BB size that does not account for this potential photo discardment / loss.
I think I'm starting to go in circles now.