Unfortunately, my experience is that any bra which fits well in the shop might quickly get too loose to support you properly!
This is because brassieres stretch a lot with initial use, and most people don't realize how tight & snug a properly fitting bra needs to be.
Also, many shops use an outdated measurement system, whereby they add several inches to your under-bust measurement to get your band size. I think this is a a throwback to cotton bras, which didn't stretch much.
I have found that a new bra should only be just about fastenable on the loosest set of hooks. You should only just be able to get your hand inside the back band. The band will stretch a lot, and one solution is to start with a bra extender.
I also find that many of my TG friends don't tighten their straps enough, leading to the curse of the falling bra strap! My rule of thumb is that with a new bra, you should just be able to pull your straps up to the bottom of your ear lobes. So on initial wear, your straps will be tight and might leave indentations on your shoulders.
Finally any new bra will be scratchy and should be washed before extended wear.
So what I am really saying is that a long term comfort bra will start as a tight unforgiving bitch, which needs to be tamed by wearing and washing!
