Well, I'm not post-op, I'm Ftm but I can answer this.
I'm built small down there too but can still accomodate most men. The vagina is pretty resilient and will stretch with practice. (if you're regularly sexually active, it will become easier, the ride smoother)
There are of course men you will never be able to accomodate, whom with you're literally sexually incompatible. A good rule of thumb is to check his crotch area before you let 'it' near you. Too thick or too long - don't let the door hit him on the way out.