Yes it is pot luck if you cant try something on.
I am going to get a size 8 and size 10 dress and that way, i will have to return at least one of them. I see this as part of my transition, as it something that i still have to get used to. I have never reurned clothes or anything else in my life and to be honest, i am excited about it. Although i may not be that excited, in a few years time.