Thanks for the provided information, I'm a fan of fully regulated drivers.
Jensen567 provided related testing on an early layout version of the H1-A plus H2-C and KX70 drivers here: Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy). His H1-A measured efficiency figures were somewhat 
better. I have an H1-A modified for close to 4A at the output (≈3.95A) with an R100 plus 2x R330s stacked over its stock R025 sense resistor, driving a dedomed XHP50A inside an SK98. The tailcap switch was replaced with an Omten 1288 and its spring bypassed, of course. The pill was also copper plated (you can check some pictures here).
That ∅22mm “Manta Ray” 2S emitter boost driver looks very nice. I'm not in a hurry for a new build, albeit it definitively goes in my wishlist. They have an interesting C8.2 host in that store. For those of you who like aspherics, this 26650 Fishing Flashlight Host may be quite nice (personally untested yet).
Cheers :-)