SHS high strength polycarbonate (already SC) is great, but you're gonna have to SS it down to 8 teeth. In terms of piston head, just use the stock one that came on your gun. Don't use aluminum heads because they can be too heavy, causing PME. If your cylinder is ported, you can just keep it. Matrix silent cylinder head works all right (kind of a pain to cram into the cylinder because of the double o-rings, but good compression). For a DSG, your spring should be AT LEAST an m150. Otherwise, be prepared to deal with some fun PME. I think you're better off with an ASG 30k instead of 40k, as it's got more torque, making it last longer pulling an m150. I think 40k will get strained more easily. Also get the gate quantum 1A1 trigger (~$25) because I've heard of stock trigger compatibility issues with the gate aster unit specifically. Good luck on your build.