I have tried 6600 6700 and 6800. Seems to run out at 6700. Launches better at 2500 and up. With the same vert my small block launched nice at 2000 with 60ft of 1.45. Lenny must have really tightened this vert up. It goes thru the traps at 6900 with 5.75% vert slippage.