I need an 18" rim for that tire, or I would go that route. Also, I made a wooden mock-up tire to the specs of that drag slick. It JUST fits in the stock swingarm. If I stretch the arm a couple of inches, like I has thinking of doing, clearance should not be an issue. If the chain clearance is an issue, then I will probably go with a Free Spirits offset primary sprocket.
Free Spirits Offset Sprocket Also, Ryk, did you see my PM a week or so ago?