If we're not planning to barrel the guy off Axxx, shouldn't we check on the flop already? Like you said, otf he's pretty much calling Axxx and folding the rest. Obviously we'd rather save the bet against Axxx if we're not getting him off the hand later on, and the hands that fold are in very bad shape against our hand. We can continue on a ton of turns after checkback, and a passive fish isn't too likely to put us in many tough spots later on.

I vote for checkback turn. reason is he not folding any A*** ott. and there are tons of aces (my guess is most of OTF calling range (depends on fold vs flop cb) I haven't done any math on it tho) 

K blocker is somewhat revelant to me too, but its not too big of an argument for 3barrel as my assumpion is - he calls w\ AKxx and A6xx OTR with same frequence (which should be rather high)

In this history, you are IP that makes us easy to check ott...or am I missing something?

I don't mind checking this back on flop.  Actually, I don't see a very compelling reason to bet, so I think I'll more often than not check this back.