So stacking off on the flop is bad but stacking off unimproved on the turn is good? I think he calls 3 bets on the flop with AT/AK/A x which probably feel less committed by the turn. Really, we're only afraid of AJ and KT. And I think both those hands probably tend to put in more than a half-ish pot bet on the turn.

If you're so convinced that he's solid just call and call. But I still think 3betting the flop was the best move.