Awesome looking build! You must be one tall SOB. I am building a Duc Monster, well, slowly. Anyway, I'm thinking I'll only extend the swingarm about 2", though I don't know anything about how to CAD it up. I'm also putting on a taller shock and an adjustable height tie rod. On top of that, I'll go with larger sprockets front and rear to help the angle clear the swingarm.
Have you seen Old Dog's Ducati build
? He went about 4" on the swingarm and he's pretty tall too, and he still thinks it was way too much from what I gather. Not sure if it was the height or the length he had a problem with, but you might want to give him a shout and find out.
By the way, one other tip for weight savings...check these batteries out:
Guys are using them on the Ducati forums with no issues. They are also suppose to last longer, and put out more power than a lead battery.