[bbartlog]

I don't think jacks and fours will hold up

True, if you get to the river. But one of the dynamics in pot limit is that you can really charge your opponent on each street. Half the time, the turn will not bring a low card - and in those cases, you will usually be able to take it down, especially if you came out strong on the flop. One other point is that while you would normally have to worry about a repot on this flop, the fact that the ace of spades is in your hand limits the possible strength of your opponent's flop fit.