I have no new info to bring to the table, but I've been wondering this too because their v-neck binders are a lot cheaper than Lesloveboat's, and I wear scrubs at work so my tri-top shows without an undershirt. I'm a small or medium in the tri-tops, but a large by peecock's size chart too. I imagine that's probably accurate since they're asian sizes, which run small, and also, unlike the Underworks binders, they're adjustable with the velcro, so a bit big would be better than too small.
The no return for sizes thing is discouraging though, especially since shipping is so high. I'd like to order two or more so I don't have to pay $20 for shipping twice, but that could be a waste of a lot of money if they don't fit.