MAK-90 modifications

[Nemesis]

Is it legal to modify the actual thumbhole stock that came with my MAK-90? Like shortening the buttstock and/or sanding down the thumbhole area to make it thinner? Also, can I put a compensator on the barrel if it is permanently attached?

[JA]

As long as it is still a thumbhole not a seperate pistol grip. Muzzle brakes permanently attached are legal.