Assumption: .25/.50 NL. Equally balanced stacks of $20. 6-8 players. Everyone limps in.

Are all preflop hands worth a call here and at what point would they not be? Considering pot odds, how many hands are not worth 7-1(or 5-1) to see a flop and how many are so -EV that even the implied odds wouldn't be worth taking a miracle shot here?

On occasion I do find a game like this and am curious how much I should be opening up my starting hand requirements without it becoming a leak.