Okay, waay late on updating this thing, got super busy with work and getting the bike done for the race. Ended up crashing my bike in the first lap of the intermediate race due to a poor headtube angle, messed up my front fork and popped the front wheel off and bent the axle on it. Sad at the time, but ended up taking the Crash and Burn trophy home as compensation, and rode Farfle's bike to first place in the unlimited class. Also, the seat that I posted earlier went on Farfle's bike, but we built up our own passenger seat for my bike from a Bell cargo rack, steel tubing, and a cut off handlebar stem to attach the support bar to the bottom of the bike. The seat itself is 3/4" plywood through bolted on with 2" of hard upholstery foam with marine vinyl wrapped and stapled on.
The battery cover was a Rockwell brand sawhorse cover that I picked up on clearance at Sears for $15. Simple mod, if slightly time consuming. Just use big wire cutters to pinch off the heads of the rivets for the steel bars that run along the sides and slide them out of a small slit you cut in the corner. Then go through and undo the stiches for the side pockets and find where the corners wrap around the bike. I experimented with several methods of applying Velcro to the cover and found that my sewing machine wasn't up to the task. If you had access to something more heavy duty it would work fine, I ended up with one strip that is half sewn and half glued with fabric glue. Seems to hold up fine, but I was more impressed by the iron-on velcro strips, which hold on much better than expected. The only thing you have to worry about is having the iron on too hot and melting the fabric.
In the end I've got a bike with a top speed just shy of 32mph and a 66v nominal 10Ah battery pack. Great project, going to be taking it with me to college and riding around with the girlfriend. Special thanks to Farfle and his dad for all of their help and the late nights that made the bike possible.
(Taken just before we did the passenger seat, wanted to show how the cover is supposed to fit.)