New Streamlight Protac HL4

It’s not budget but its new and bright. Of the damn near hard to destroy or break lights I have, it’s been Protac and ArmyteK. Now Streamlight has gone double 18650 on a new very bright light. 4-CR123A’s is kind of expensive but two quality 18650’s and it’s my new do about everything light. Just thinking now if I can get that HL4 head to fit the HL3 body bored out for 2-18500’s as a new rifle light or just a nice chopped super light. By the way does anyone know if the HL head and body are interchangeable with the HL3?

http://www.streamlight.com/en-gb/product/product.html?pid=342

Soo, XHP50 or MTG2?

Out of all of those data sheets, I couldn't find what emitter is being used. They always say: "C4 LED technologies" but never list the emitters.