Yes the knees should be behind it.
Apologies, I haven't read this entire thread; perhaps this has been addressed: have you any idea how much this might reduce drag, hence increase mileage? Am hoping, when finished, you will post enough info for others to build.
Anyway, I'm fantastically impressed! I really think Zero should spend a year or two working on aerodynamics. At this point performance is superb and range is impressive (SR). If they could improve range by more than 25% just by offering a fairing such as you've designed .. that would be a HUGE win for the company.
My data point for aerodynamics is my 2004 Aprilia 500cc scooter. Boring acceleration ... but I get 60mpg at fast highway speeds. 'Course, now that I have a zero, I don't ride it much ...