It's kind of irrelevent that ak is slightly behind his 5 bet shoving range because the vast majority of the time he's going to fold to your 4 bet, his 3 betting range in this spot should be fairly wide. In regards to the sizing, I don't think it makes much difference due to the frequency he'll be folding, plus it leaves more room for him to spaz, though I do get where you're coming from, having him flat the 4 bet and the flop coming q97 would be most uncool.