gettin too technical for me but i'll save this page to refer to. Can use it now to work out my 70x70 stretched DT1 & 80x64 shrunk RT2, or for that matter my destroked overbored TF100 bucket racer [not run for years] using a crank [one side] from an RD200--52x46.5. Forgot i changed it to a 125 cylinder in the end so 56x46.5. But 'dumb me' not thinking--when i had my husky chainsaw apart, remember looking at the crank & measuring from centre of pin to centre of crank, looking at the verniers & thinking jeez how oversquare is 'that' [then i woke up].