The Viper is a very good plane and with some strength and incidence mods it can become fabulous. I'm on my third ship. the first two died spectacular deaths due to structural and on board control failure. let me pass on some of what I have learned. Throw the stock wheels far away. All three planes needed the V tail shimmed up at the rear, I start with .040". You'll know when it's good when the tail's control surfaces are about flush when trimmed for level flight. Failure to fix this incidence problem could lead to servo failure or shorten battery's run time due to the constant load in flight. Just like a stalled throttle servo can do to a battery. Use a plastic push rod (like Goldenrod)and plastic ends on the throttle control, this will reduce the servo killing vibration. Before installing servos, drip in thin CA into all the little gaps around the wing mounts, formers and bulkheads(do this outside in the sunlight and fresh air). Add a 1/16" x 1/2" piece of plywood to both sides of the upper edge inside of the rear servo/batt compartment. You won't like this part, I remove a strip of covering material on both sides of the fuse to allow me to CA a strip of .014"X 1/2" carbon fiber 4 1/2" long that starts 1 1/4 ahead of the leading edge of the wing and running just under it. And again a 7" strip that starts 2" ahead of the leading edge of the V tail and running just under it. Then recover with Monocoat. I use BLUE Locktite (removable) on all steel screws. I use Locktite each time I put the wing back on. And no, I won't go to plastic wing screws! Use a timer on your flights,( I use 4 minutes) this lets you dictate engine shut off to set up for planed landings. Run the fuel out of the engine and use after run oil when done.