Only thing I can add to this is.
If you get a 6.01 barrel you will not need any nozzle over a black. Otherwise you will be shooting over 375 with .25's
With that being said. The FCU is very delicate. be very careful if you put it in the hand guard of your weapon. Polar stars customer service is great for questions as well.
Last thing. If you buy the Polar star (VFC made) complete kit. You will have to buy an adapter for the air on the gun to fit the air rig.
All said and done a polar star with two air tanks, & Air Rig will run you a little over $1100.
Polar start kit $625-725
Air rig $120 - 150
Air tank each 49.99 1400 shots @ 120PSI &3.00 to refill HPA ONLY!! (Compressed air)
adapter from HomeDepot $4.00
Accessories like a new MOE Mad-bull hand-guard $40.00
I also recommend getting a 9v Duracell and wiring hardness for it and using that to power the FCU.