Well, I finished my homemade light system based on the Optronics MR16 fog lights and everything is working fine but wanted to share some information that may be useful to others.
1) System designs, specs, and construction: I basically followed the advice give in this thread and here: http://nordicgroup.us/s78/
2) Battery pack/holder: The best packs I could find were small digital video camera packs. I found one at Walmart that was precisely the size I needed to hold my 5HA battery. The battery goes in the large compartment and the switch and fuse go in the smaller one. The pack hangs from the handlebar with three Velcro straps that you can buy at Lowes or Home Depot.
3) Clamps: I ordered the Minoura bottle holder clamps to attach the lights to the handlebar. These clamps are great as they allow you to direct the beam not only vertically but also laterally. Well worth their $3 price.
4) Bulbs: I ordered 10W (narrow flood), 20W (spot), and 35W (spot) bulbs. Of these, I ended up liking the 20W and the 35W and will use one or the other as needed. I did not see much value from turning on the 10W bulb even as a second light. I will only use the 10W if I need more run time from my battery.