A LiCo AW 16340 should be like other LiCo chemistries -- good for up to 2C max discharge rate, or about 1A. A 6x7135 driver is too much for that cell. An AW IMR16340 is good up to 8C discharge, or about 4.4A.
However, if you want to get max lumens from a triple XP-G, you need to deliver 1.5A drive current, which is the max recommended in the XP-G datasheet. For 3 in parallel, that means a 4.5A driver. If you use a 7135-based driver, that means that the cell will have to support a 4.5A discharge rate. That exceeds even the IMR16340. And even if the IMR16340 were discharged within spec, the run time in regulation will be essentially nil. At 4.5A draw, an IMR16340 will stay above 3.5V probably for about 3 min (see
here for IMR16340 discharge curves).
For three XP-Gs in series, you need a boost driver that can deliver 1.5A drive and boost ~3.7V up to ~10V-11V load. You are looking at ~15W right off the bat, and that ignores the fact that drivers are not 100% efficient. If we assume 80% driver efficiency, you are looking at about 19W. A single 16340 is roughly 3.7V*0.55Ah = 2Wh. You will get a calculated run time of ~6 min. Of course, this also assumes that such a boost driver exists.
If you really want to drive a triple XP-G at max lumens, you need to re-think your battery configuration.