I'm using the same optronics bulb case (only one) with a 20w bulb. it bolted right on to the fork bridge on this Downtube folding bike I recently bought as my full time commuter. Velleman xenon strobe on the rear and I am using a 6Ah SLA battery that comes pre-packed as the "Vector portable Power" unit discussed very early in this thread - which includes an in-line fuse, 12v accessory outlet and water resistant case. with the 20" wheels, the battery pack fits neatly under the rack so I can still have the child seat for taking my daughter to day-care. I am very happy with the setup and all the advice Ive received here. Just bought my switch and some more wire to get things routed more neatly, but it's pretty much done!