With all that has been said between Dale and JasonWW I see that it is in agreement (basically) that the XP-L HI IN A FLASHLIGHT will be doing around 1200 lumens at 4.5 amps.
With the steady current bench power supply , that is all great to see just what current an emitter MIGHT handle , but it tells us nothing of what the emitter will do in a flashlight of any kind that I can see.
When using the bench power supply and heat sinking it with a chunk of copper or aluminum and a fan to cool the emitter , then I do not see where that will any where near replicate “real world” use in a light.
With the XP-L HI in the lights I have modded , I would say an average of 1050 to 1250 lumens is about where the mini GT and most other lights will be as a guess from prior experences with the 4.5 amps. Of course it will depend on ALL those varibles of what type springs , the cell used , other resistance points and so on , as to the final output.