[vmacosta]

you are getting 9.5:5 to call down so I'd say a decent rule of thumb is to continue with anything that has 1/3 equity.
You guys can stove it for yourselves but that makes most rainbow boards with two bway's profitable call.

To solve this more generally, I'd suspect we need to figure out which flop+turn+river combos will make for a river fold and then work backwards (i.e. which turn cards should be folded given that we will be able to get away from our hand on the river so often, and then which flops are good given how often we can get away from our hand on the turn or river). This all assumes he always bets when checked to. If he sometimes chks behind then we should be peeling an even wider range (perhaps any flop where we have 30% equity).