Blevy
I don't have one so I cannot confirm it , but if you look at the pics on the TT site you can see that both sides at the end have a mesh just for that reason (to prevent your bag from touching the fly)
In my experience with the TT it will also be rear to have condensation in that area ( as in that low ) and looking at the size of those vents it would seem even less likely with the Moment.
Can't remember how tall Eric is (300Winmag) but he has one , so he may comment on this. He also has used other TTs so could offer some good insight.
Franco

http://www.tarptent.com/moment.html