I had the big hookworms on a 25mm rim and it still looked kinda silly. No issues with the tire rolling off the rim, but I didn't really push it performance-wise.

Why Hookworms? Because they are awesome. 2.5"!!!!1!!

(I got rid of mine, too heavy for 38mi r/t commutes, 1250g/ea, there are wheelsets which weight less than one tire... If I had a short urban commute or it was on a spare bike, maybe.)