Since I had the parts laying around I decided to try and fit an MC18 swingarm into my MC16 chassis. and along with that an MC21 4.5x17 rear wheel. Everything fits pretty well as the swingarm pivot for the 18 is slightly narrower. Currently fitted to the wheel is a 165/60-17 slick. Biggest issue I see is the right muffler fouls the swingarm so I need to move it outward 1/4-3/8" for adequate clearance.