I doubt you'll get 3 x XP-G's in a normal lumi can running at even 1 Amp, the heat output is quite significant aftet all the LED's are only 20 odd percent efficient so 70 odd percent of the energy does into heat, 3 x XP-G's at 1A consume 10Watts, so 7-8 Watts of heat into a small can . . . and there is your problem, however my intention is to do this in a lumi HID can which is another thing altogether, much more mass, much more surface area and handles 3 x XP-G at 1A no problems whatsoever . . . I don't expect problems even at 1.5A . . .
Also remember that, certainly from my POV, not everybody is using tiny wee 2.6Ah batteries . . . I have a number of 4Ah NiMh batteries so reduced runtime at full power reduces is to 2.5-3 hours rather than 4hours at full boot . . . 😉
The heat dissipation with these small cans is the killer . . . hence why the conversion here uses lower currents and hence produces lower amounts of heat . . . of course they could be brighter, but the heat will kill them . . .
I an planning a simple on/off 3 x XP-G at 1A in a lumi stock lumi case, but will be bonding some finned heatsink on the outside of the can to keep temps under control . . . I'll take the risk that it's the big rock or tree that will hurt me rather than a tiny wee lamp heatsink 😉 . . . a practical, small, 1000 lumen headlamp is what I am after to go with a big floody bar light . . . I don't like only one lamp on the bike, you can't see round corners 😉
When you look at the lumi cases designed for LED's (some pics of a LED 3 appeared at some point) they have quite a minimal case, certainly smaller in almost every way than a converted HID case . . . hence my choice to use HID cases . . .
Anyways . . . fun and games 😉