One of the ADVANCED SERIES of kits, which include factory pre-slotted airframe and through-the-wall fin construction, the 3.9 V2 is our sport scale version of the infamous WWII German V2 rocket. This boat tail kit comes standard with a 38mm motor mount but flies great on F59 and G motors using an optional MMA-2 adapter. The 3.9 V2 is a great performer on a variety of motor packages through Level 1 - For Level 2 motors and large Level 1 motors change the launch lugs to rail buttons to eliminate "rod whip" due to its short height and wide motor mount location. Parachute Recovery.