Been some people converting them to run on 9oz. paintball tanks (ditch the detachable fore end, mod the stock a bit, and get an AS to PB adaptor) Internal mods. seem to be centered on spring force, at least so far...suspect it's not nearly as mod. friendly as QB's.
Usually not a big fan of "wack the valve harder" as the only way to more power...the .22 versions seem closer to advertized vel. than the .177's and I'd probably be happy if it could be easily gotten to an honest 650fps.
Internal debate: Might be a winter project...then again, other than the magazine, what would it do that a QB79 wouldn't? Do i need that magazine.