Just cuz I fear people aren't necessarily getting this. The shortcut for how much equity you need is to take the bet and divide it though bet+pot. So (2/3)/(1+2/3) = 0.4
If you were to bet half pot it's (1/2)/(1+1/2) = 0.33
So if you could make him fold underpairs to a half pot bet, it would be profitable. - Less marginal than it looks because you can still improve your hand.