Well, I think they really aren't supposed to touch your foot at all. I think they will actually stretch somewhat, but I don't know if I would buy them, if they weren't comfortable from the beginning. Also, I have had mine actually shrink. They were left in my car, and the right one actually ended up 1 inch shorter than the left, and no longer fit. These were the flip flops.
I actually know just what you are talking about. My feet are big anyway, so I hate wearing shoes that are too large and floppy. I have a pair of Beach
crocs that make my feet look even more huge (and hot pink was the only color in my size- which didn't help!) and so I wear them only in the house, like slippers- so comfy.
The Caymen style looks just like the Beach style, but I think you can order it in a more exact size. You may need to order it, as I don't think I've seen it in stores.
I really like the Athens flip-flop, and I am not really a flip-flop person, I usually hate the between-the-toe strap. But this one doesn't bother me. I find them just as comfortable as the beach or caymen. Anyway, I can actually get away with a little bit smaller size with them, since they are open-toe. So I don't feel so much like I am wearing clown shoes.
Good luck- I LOVE my crocs!