I figured given the size of the trd 19's, in both height and width, that larger tires would work up to a certain point. I've toyed with going as big as a 225/60/16. But 215/55/16 would fit no problem I'd guess.
When it comes time to swap the summer wheels on, and if I have a 225/60/16 around, I might try one just for the heck of it.
I've toyed with the idea of going to the white wall look full time on bags, and I'd want to tuck a larger tire more looking like an old hot rod, that size would fit the bill and is also available in WWW.