The first couple of A5s I ordered from McM had thumb wheel adj cheekpieces, which worked fine. But the clampbar adjustable integral cheek piece is lighter, doesn't rattle, and has no locking screws to come loose and/or fall out. Did a rifle for a customer who showed me the KMW hardware in his Manners stock, and decided that was the way to go. I've got several McMs - mostly A5s & one A3-5 - with the McM clamp bar mechanism, and am pretty well satisfied with it. It's dirt simple to remove the CP before cleaning a rifle with the clamp bar set-up, and easy to replace it when you're done.
Have thought about taking the time to machine grooves in the front post of my McM clamp bar cheek pieces so I could use an 'E' clip and essentially have the same set-up as a KMW, but honestly, it just doesn't seem like I have a problem getting the cheek piece adjusted to suit when it's time to shoot.
Does stockdoc convert non-adjustable A5s into adjustable ones by cutting the cheek piece out & 'glassing the cut surfaces of stock & CP? I've got a nice desert camo A5 on a 280 AI that I'd like to convert if it's feasible.