limping in the SB

[LtJDangle911]

i've come across several posts and articles which teach how to defend the SB, but are there any pieces of advice on when to simply limp in the SB?

for example, i imagine that limping in the SB with A3o is a much better idea when, say, only 2 other people have called because if you flop an Ace, you probably don't need to worry about the kicker as much as if 4+ people limped pre-flop.

on the other hand, i would suppose that limping in the SB with something like 67s would be more +EV with 4-5 callers rather than just 1-3. does this make any sense at all?

are there any links which list hand ranges to limp in the SB, or are there any ways to calculate specifically which ones are +EV or -EV?

Thanks!