I run a 540, 6.5 turn motor also. My track might be slightly bigger. I don't think I could handle a 550. I run about 135°-140° after a 6 minute main. The 1st place guy (black truck) is a factory AE driver running a 540 also. He comes off at 180°-190°with his LRP. I'm in 2nd with the white and green truck.