I have just started eyeing the blue Slim Carly. Saw it in person and fell in love. Here's my question: On another thread, someone had mentioned that it slips off her shoulder a lot. Does anyone else have that problem? That would, unfortunately (maybe not for my Visa ), be a deal-breaker, because I'd never want to carry it. It was hard to tell if it would be a problem just from trying it on in the store. It does have that little rectangular piece of leather on the top of the strap, but I don't know if that would help or hurt the issue! Any help would be appreciated!!! TIA!