[calidris]

I'm thinking that he has a J or a FD as likely holdings. He's probably not cold calling 55 or 77 PF so I consider them to be less likely. If he has a J it would be paired with at least a suited Q to cold call PF.

If he's got QJ or AJ we are drawing to runner runners and the pot is not laying us good enough odds for that. If he's raising a FD we're in better shape and could call and maybe (as I mentioned) donk turn.

I can't really see any more hands cold calling PF and raising the flop often enough but I'd be happy to be proved wrong. I've never played 1/2 and maybe people behave differently there than in .5/1 when I currently am.