I have a WE Hi-Capa that I've been modifying little by little. I added a Madbull punisher compensator, Nineball lanyard loop, TM 50rd mag w/ a Shooters Design metal base plate, and a Hogue grip sleeve. Haven't changed any internals yet, haven't really needed to. Except for a higher ammo count, no real performance upgrades but the chrome flash does make it stand out. Airsoft International had a Hi-Capa project running about a year ago, so you might find it in their archives.