Be aware, these gearbox's are designed to be used semi auto.
Also, you have to use a systema hop chamber, and high quality mags. Systema themselves recommend proper pts PMAGs.
Ailment of the gearbox is a problem too. It's made to fit tm receivers, it won't go in ca, g&p ones etc without modding.
As for rear wiring. You can have it rear wired but because of the fuse placement etc, you'll have to use a solid stock...
If it were me, I'd save longer and just get a sck. It's more money but it'll be less hassle and have more features.