Spent the day at the range with my CZC +20. Started with it on a 30 round mag body. Was jamming constantly, seems like the follower is getting hung up on the transition from the extension to mag body. Once past the extension it worked flawlessly so clearly getting jammed up in the extension. Tried another 30 round mag body and the same issues. Spent a little time with a file working on the transition between the extension and the mag body and it got a little better but still had jams. Switched the extension over to a 20 round mag body with a 30 round spring and it ran flawlessly.
I am hoping with a little more tuning I can get the 30 round mag body to work.