Originally I was going to ask for advice on this hand, but I think I figured out the definite answer for myself so I'm going to post it anyway and maybe it's a situation that newer players can learn from. Who knows, maybe someone will tell me I'm wrong too because of something I might have missed.

I was in a situation with 66xx where I flopped the underfull 969 against a decent player in a multi-way pot. I check, someone who was not the raiser pots it, there are 2 folds behind and now it's me. I shove, not really sure what the exact numbers were, but I figured I was a small favorite because obviously he had a 9.

His hand is obvious because he's not potting quads there into the table and he can't really have any other hand. And all 3 of his kickers would give him a better boat. Anyway, long story short, I later found out that my hand was 58% on the flop. So I guess whenever you flop an underfull and are pretty sure your up against trips, you are at least a 58% favorite (maybe more if he has a pair?). Once in a very blue moon he can have a hand like 96xx, but since there is only 1 other 6 in the deck, that's rare and probably evens out when he has a pair in his hand, so then maybe 58% is almost an exact number.

Then there is also a chance that they'd fold trips to a shove giving you decent fold equity here too. So HU, it's always a shove/re-pot is my point. Anyone disagree, am I wrong?

Oh, and in the hand, he snap called and hit his kicker (Q) on the river. He had Q942ds.