The 65 may look more unbalanced, but the 85 is not going to be any better balanced physically. In fact, it’ll probably be worse. If you’re only using the BTX at 30x, I’m not sure you’ll notice that much difference between the 65 and 85, except perhaps for a couple of minutes at dusk.It is nice to have the compact 65 though it looks a bit awkward on the BTX.
Also, I don’t understand switching the balance rail for the gimbal. They do different things. Once you have the scope well balanced, the gimbal will keep it there regardless of the orientation. But you still need the rail to get the balance right in the first place (at least you do with the BTX).