Havent handled a mako yet.

I dropped off the factory stock and a Mossberg butt stock today to the machinist for him to mess around with and give me some ideas. I see what you are saying about the possible flex in the pistol grip portion but I have a similar stock on a Mossberg 500 and on a H&R handi rifle and have zero flex. As of right now, I don't foresee it being an issue. It very well could be though.

I am not opposed to using an AR setup but if the Mossberg will work it will save cost in the machining, material, and actual cost of the stock and pistol grip itself.