i have a carbine with an A2 upper that has a 1/9 HBAR 14.5" barrel with a phantom FH tack welded in place. i am wanting to replace the upper with a flattop and while i had it apart, i was wondering what it would cost/ effort it would take to have my chromelined barrel cut down to 13.5" and have a noveske kx3 pinned on? also thinking of adding a 12" FF rail ontop of this. any problems seen with the barrel work i am suggesting? should i rethink any part of this?