I just got done with some club racing tonight.

Fresh built Worlds kit with Steve's setup (minus BB shocks and carbon), 17.5 Revtech 12.5mm, 75/33. Green Hybrids, JC Medium foam, kit Proline front tires.

I added the kit rear ballast weight, and 1/4oz weight on each side of the servo in the front triangle pods. Shorty pack 1/2 foam back from servo, slight toe out.

Car had a slight push on-power exit but entry and mid corner steering were great.

17.5 is all about getting the gearing right for where your motor likes to be run at. Find that and you should be fine.