Yes I ran 17.5 from December to April 8th except for a one off carpet race. Now I am moving outdoors for the summer season and nobody near me has 17.5 so switching to the 8.5 for summer. At this point yes it is has been better with the 17.5 motor, I ran 17.5 spec class and Mod SC with the 17.5 in the truck. Trying to find a good outdoor setup with the 8.5.