Another way to do it, with a modified H1-A boost driver and an in series triple. Jensen567 example(s): #19 in Buck and Boost Drivers, Testing, Modding, and Discussion
The H1-A can reliably handle 2.5A for a triple, ≈25W, maybe a tad more but it may start having trouble with its 10A input limit and non-heatsinked driver ground plane (because of reverse polarity protection). To me this is no problem, that's already a nice lot of power for an E2L, and you attain fully regulated modes in a truly useable light without having to worry about blowing up emitters, PWM and other *cough cough* driver nuisances.
Cheers 