The AA XLP works fine. I run one on my 10.5 Blackout and it cycles everything. Trick is the lightened carrier to handle reduced powder charges and reduced dwell times. That's likely the reason for the 11.5" requirement is the dwell time. Not an issue with the AA. I like that you can use any gas block you like with the Osprey, but the AA is low-profile as well as adjustable. Love mine.