This post has a link to a driver that can be used, but you would have to add 7135's: johnm post. The driver is 20mm, 1 sided, selectable modes, regulated (Nanjg): I-O driver here. Also, interesting info on the XR-E R2: here at end of opening post, showing it's lumens output peaks at 2.1 amps. With that driver, I'd piggy-back all 3 7135's.