This doesn't answer your question on swingarm length, but using this calculator will most definitely help.
Sprocket and Chain Length Calculator
It did help, never seen it before. Thanks. Ended up at 106 links. Swingarm length is at 540 at 15/41 with 106 links. The axle ends up at 6 o'clock in the eccentric which is a good start for gearing changes.
I can't wait to ride it on track again with the longer wheelbase and better acceleration.
i went down to 15T, can count the links later for you...