Hey Dez, have you tested your volt reg?  When i tested mine, it was still allowing up to 18 volts which would fry every LED light i threw at it.  Only would get about 10 minutes of working time depending on how hard i was riding.

I know the regulator was somewhat working because I tested a friend of mines system and it was reading over 100v. We replaced the regulator and he was getting in the neighborhood of 14. 

That light looks expensive so i'd be really careful.  Maybe convert to DC?  Ricky stator will build you a rectifier or i bet you can use the lt80's.