If you want a good value package for the Viper .....
Thunder Tiger 46 pro
add a Jett Stream Muffler.
Turns a 9x7 up around 16,500-17,000 peak ground rpm.
D1 series props 8.8x8 or 8.75x8W around the same.
About $150 total.
If it does not match what the Rossi runs at, it is pretty close
