Well I did give it a try today, sort of. I was in the mood to get out one of my dildo's and see how it would work being belted and all. One of my questions was whether this belt with the continuous crotch band would allow anal sex, meaning being penetrated. I had assumed that it would be difficult, but not impossible, and I was correct. In the interest of scientific research :) I tried using a dildo that is pretty realistic, with balls attached to it. In terms of shape, it's pretty much an anatomically correct version of your average man, not anything huge. Plus, this one had the balls on it, so I figured that would give a good representation as to how far it would allow penetration.
For obvious reasons, a normal person's balls would not fit through the anus hole on the belt, so this will cut off the possiblity of full penetration, by about 2 inches, but penetration is possible. So, the verdict on this would be that the belt prohibits full penetration, but allows partial. Figured I'd let you all know that.