I got my 6-9 718 AP2's, and added an AP3 5-iron to play with and see if it would work in place of a hybrid (spoiler... days are looking dark for the 5 hybrid). One note: I had the 5-iron made 2 degrees weak. It is only a 3 degree spread from the 5-iron the AP2 6-iron, as opposed to the 4 degree spread between each of the AP2's and subsequent wedges, but I've found that the yardage gapping is actually perfect.
My hypothesis was that people were saying that the AP3's added a good couple yards so I wanted to make sure my yardage gaps stayed at what I was used to. Conclusion: the hypothesis holds up better than expected, and yardages look good.
Just wanted to post this in case anyone was thinking about an AP2-AP3 mixed bag.