I would not recommend the viper 17.5's. They aren't known for being a good blinky motor. If you want something that everyone else has then the reedy is good for blinky. The d3.5 is technically legal...until march I believe when it gets taken off the legal list once again. The new Novak Vulcan motors are very good, and super smooth. I would start gearing in the 72/33-34 range with timing pretty much maxed out (for either the reedy or Novak) and check temps from there.