Playing .10/.25 zoom a while ago a reg / lag (31/17) opened pot (.85) first in and I flatted kh7h5s4d in the Co. In retrospect this is too loose, yes? Roughly what % of hands do you advise flat calling with in this situation? What would be the best hand you would just call with here, and what would be the worst? (Or conversely what would be the best hand you fold?) Button's stats are similar to UTG's. BB looks nitty and SB seems like a pretty loose reg or maybe a tight fish (46 VPIP over only 36 hands).

Effective stacks are just over 100 bbs.