question about sizing

Yo, question to anyone who has bought things from the FBR store before?

For instance, I buy a girly large tshirt from threadless. Looking at the sizing charts for both places, that looks like a adult small from FBR. Which is the size tshirt I'm supposed to get with my Panic stuff, but god knows when that'll get here to try it on, and there's a sale on now. And should I go for a small or medium hoodie? And why doesn't the TAI Heavy Heart long sleeve tshirt come in adult sizes - I suspect trying to squeeze my tits into a girls large would be inadvisable.

Really, I should hide my wallet from myself when I'm in this kind of mood, but c'mon, enable me ;)