Hi!
I did a very similar thing to my rough cut (seal improvement, spring replacement, sealing the upper barrel holes, your 2x4 conversion, attaching an adapter to fit it under a buzzbee brute). Your 2x4 is working nice, i just cut smaller connections. I can half-pull for 2 at a time, full pull or even slamfire it all in under a second.
Whats your latest on the speedloader? Would it work, if you cut the middle and one side with a knife so you could "rip it off" to the side?
Like: plug, rip, done?