i race rcgt in omaha nebraska at the hobbyplex. its an awesome facility with a fast carpet track. we use x-patterns, 21.5 and an open speedo and its fast. 21.5 and open speedo is probably the way to go. and as far as the ff03, the best motor for it is the 21.5. the silver can that comes with the chassis is equal to the revs of a 17.5 with the torque of a 21.5 so i would do like i do and just run a 21.5 and a spec speedo. its a lil slow on a long straight but it kicks butt in the turns!