i personally have never ran a piston setup, i've only ran DI so i cant give you first hand experience, i went to CMMGs website and couldn't see how their handguard mates to their receiver. I don't know if Adams Arms will fit because typically they make you run one of their handguards, i went to syrac ornances website and saw that they had a pistol length piston, and from what i have heard their piston was designed to fit almost all handguards, if you go the piston route look into syrac because they also have a fine tuning gas block that will allow you to dial in your gas exactly where you want it, i could see that being a benefit running a pistol length gas tube and maybe lightening up the recoil impulse.
link to syrac ordnance pistol length piston- http://www.syracordnance.com/products/retrofitpistonkit-2
link to Adams Arms- http://www.adamsarms.net/pistol-pdw-length-piston-kit-xlp-no-rail
link to Adams Arms compatible handguards- http://www.adamsarms.net/faq#qa3