I think the Charlie stock works better on my SU-22 than it did on my SU-16. Not that the .223 kicks much, but somehow the Charlie stock seemed to have not enough torsional rigidity on the SU-16 for my liking (although I love the underfolding design), but the Charie stock is much more acceptable on a light weight survival .22 rifle. That's mostly my preferences and as such, very subjective. YMMV.
The Echo stock (AR pistol grip) would be great on the SU-22.
I think when Kel-Tec releases the side folding stock, it should be very good on either SU as well.
Still on my SU-22 To Do list:
1) Smaller and lighter scope
2) Use see-through rings and reinstall the rear sight
3) Matte black Ceramacoat on the barrel and gas tube
4) Pull ring on a stainless assembly pin
5) Custom waterproof padded carrying bag
6) Waterproof wide mouth polycarbonate ammo jar
7) Two inch butt stock extension
8) Bi-pod?
9) Bench rest ammo test to determine best accuracy
10) Bayonet (just kidding)
I took a couple of newbies shooting on Sunday. It was cold and cloudy, but we had a great time. They learned on the SU-22 and then shot the SU-16 at the end. That SU-22 just keeps getting better. Opening the lower edge of the ejection port drastically improved performance, which now seems to be 100% with decent ammo. the new SU-22s should have the opened port from the factory. With cheap bulk pack Federal ammo, it shoots about 2 MOA, and it'll probably shoot a bit better when I put it on a solid bench rest.