The L1 heads are "dumb" that is to say, no converters. They are in a direct drive configuration. Putting the Cree XR-E on the L2 is likely quite detrimental as the L2 is designed to boost the 2x123 supply to a voltage needed to drive a 5W Luxeon at ~700 mA as I recall. You would want a buck converter in the L2 to drive the Cree XR-E.