ok first i like the great planes viper they fixed the 123 mines 0-0-0 now [8D] the servos will work the tank works better on the cg if its a bladder tank i would go with the bladder tank if not for any other reason than there more trick than a stock tank
and the battery will have to very small like a 250 mah and go really fast[8D] OK FORGOT THE ENGINE PART THE 46 FX WILL BE FINE THE 40S WERE USING MITE MAKE YOU LOOK AT IT TO MAKE SURE IT DON'T SAY COX HAHA JUST JOKING I JUST FLEW MI FIRST Q 500 TO DAY HANG ON