Okay, figured it out. The stock isn't designed to pull-off the buffer tube. In order to get the stock off you have to drift the pins (2) out of the adjustment lever and the position locator rod (1). Once it's apart you can clearly see it wasn't designed to come off the tube in the fashion a normal AR butt stock comes off the tube.
I took it apart so I could fix the loose and sloppy fit of the stock on the buffer tube. That fix turned out to be easy. Two layers of 'Gorilla Clear Duct Tape' on the top and around the sides of the buffer tube was perfect. The stock still slides but with mild friction and there is no slop in the fit once you have it in the position you want. So nice.
Fired over the Chrony today. The AEA 22gr were averaging about 930fps with the factory tune. I expect dropping that velocity to about 900fps will give slightly better shot-to-shot consistency??? However, I probably won't change anything as I plan to move on to slugs once I am familiar and comfortable shooting the 250Z. At that time I'll start tuning.
Rifle is getting 38-shots from a 3650psi fill before going off the regulator. Regulator is set from the factory at about 2050psi.
The AEA 22gr pellets have a head size of .219" and I can definitely feel it pushing the pellets into the breech. I think the rifle might do better with .217" projectiles??? Time will tell.