RE: Viper 500 flight problem
Rchad, This seems to be typical with the Viper. It is funny I was just test flying my new Nelson powered Viper today and experienced the same thing. Does it look like a jump, up or down? Like it is unstable in pitch? My Viper with a TT .40 did this as well and moving the CG forward solved this. I had my CG at 2.75 from L.E. . I started off with my new Nelson Viper at 2.75 and it still did it though. I think at those speeds I need to move it further forward as well.
While you could be experiencing radio issues I think most likely it is your CG.