I may do a larger write up on this, but here is what I did to make a 12rn AW mag. I shoot PRS "weekend warrior" and used the the CDG for most of the season last year. I lost out on lot of points because I could only load 10 rounds. With the factory follower and running 6CM, I could load 11 rounds and I was pretty fast on a single load from the quiver, so I never put too much thought into modifying a AW. Then when I switched to 6BRA and the HRD mag kit, I could only load 10 rounds and then a shot a lot of matches with 12 round stages so I decided to look into a mod. I read the posts by 375Max in which he made his own, with a whole lot of machining and welding work. I do not have that type of machinery or his knowledge, but I do have a Dremel.
All I wanted was to fit 12 rounds, not more. I believe 375Max can run 14 with his design. I purchased the Area419 ACIS mag extension, which slides right onto the bottom of the AW mag with no modifications. I took the follower, traced it on the bottom of the AW mag, took the Dremel and cut the plate out so the spring would rest on the mag extension, but the follower would not pass the bottom of the mag. The spring in the HRD kit is longer then the factory spring and I think that helps the mag run properly. Once I put everything together, I loaded up 12 rounds. The 12 round, there is very little movement, but there is a little, enough to operate. It was cycling fine, but then I thought about the waisted space in the mag extension. I ended up placing a 1/2" piece of white plastic in the bottom of the mag extension which provided a little more tension with the follower. I also added a brass nut on the Allen head bolt that keeps the mag extension from sliding off. The mag ext could move because of the bevel on the bottom of the AW. I would like to switch the nut to a oring.
I did this mod late last year, but wanted to test it before writing anything up. I finally shot a match with it a couple weekends ago and it worked flawlessly. Probably shot 6 stages with it, in terrible weather with zero issues. That also goes for the CDG action. I have probly shot 10 matches with this action and I absolutely love it. As far as a competition action I can not find any real faults with it. The only thing that I do not like is that I can not use my MPA brass catcher due to control feed design. Depending on how hard you run the bolt, the brass will eject at different angles and cause a malfunction.