Nice job, and it's good seeing a street legal setup (would be nice to see a forum of street legal bikes, for those of us who have to go all the way). If I did internal gearing, I'd do a internal geared hub on the front wheel, but no clue how well it'd hold up.
Either that or I'd try what I been dreaming up the last few nights. A skinny four wheeled (to help with engine support, provide more footing - just get off, lock the handlebars facing forward and it's parked) carbon framed bicycle, that would shift side to side (turning left would lift the left wheels slightly, turning right would lift the right wheels slightly) as you turn (front wheel drive so the gyroscopic effect works for you and you have better fuel efficiency).