Just finished my wheel mod. 5” castors on the front and 12” fixed wheels on the back. Using 12” wheels keeps you from trying to drill the old axles out. Just cut them off, your wheels will be above the old axles
Made a great wheel mod on my newer RT700. Used 5” castors on the front and 12” wheels on the back. This keeps me from trying to drill the original wheel axles out. It puts your hole above the original axle. 1/2” axle and locking collars to hold them in place