Hey guys, I'm Evan, I was the R&D Mgr & Engineer at Electrosport Industries up til last April. (Was laid off when the company went under...then screwed by the new owner, don't get me started...)
Anyways, I'm really familiar with the Acewells. Electrosport was the US distributor for them. I'll be using a couple on my R90 build (see my sig for link). If anybody needs help or has questions about them just let me know.
As for the 2800 series (round housing like bpeckm used),
You CAN use the Gen light (its actually a hazard light indicator). You'd have to take the housing apart.
The outer ring on the 2800's does come off, use small screwdrivers to pry the ring off. You can then pop out the unit from the housing.
You can isolate the ground for the gen warning light, and use it for the gen function. you'd have to solder to the LED itself and run a seperate wire.
If you have other questions, let me know!