RE: GP Viper 500 - flight report
Looks great, I would suggest a couple pylon props for that combo.
Both the 8.8"x 8.75 and 9 1/2" x 7.5NN work well and should get you up closer to 120 mph.
If you want max speed an 8.8" x 9.5 works well on a long pass, but is tough to get off the ground and loses a ton of speed in a hard turn.