A LifePO4 cell will be 3.6v fully charged.The instant a load is put on it it'll drop to 3.2-3.3v(depending on load and ir) so the light will never see 3.6v. It's not like a lithium ion that steadily drops. That is the same as two fresh lithium iron disulfide cells so it'll be just fine
Apologies for sticking my nose in here, but not quite, vivc; I know you know the knitty gritty, but accuracy may be important. LiFePO4 cylindrical cell termination voltage is 3.65v, but many smart chargers don't show more than one significant digit, and will display a 3.7v termination voltage when charging is complete, presumably the termination voltage is still 3.65v, but the display will round it. I only mention because manufacturers and retailers are now using voltage specs to identify cells of different chemistry, "a 3.6v cell, a 3.7v cell" etc. Generally speaking, an advertised "3.6v cell" will either be a primary lithium cell that has about that voltage fresh, or a secondary Li-ion chemistry that terminates at 4.2v fully charged but rides 3.6v under load for most of its discharge profile, or averages about 3.6v for the same. A 3.7v cell will be a secondary Li-ion chemistry cell that terminates at 4.35v fully charged, but rides close to 3.7v under load for most of its discharge profile,or averages about 3.7v for the same. Hope you see why I posted. LiFePO4 secondary cells are advertised as 3.2v cells, not because the charge dips to that under load (whether it does or not I have no idea), but because after a LiFePO4 cell reaches charge termination of 3.65v, and then fully rests, it will rest around 3.34v–3.42v, but for most of its dischage it will hover around 3.2v no matter what the charge at rest is. /pedant
edit: slow route, HKJ beat me to it, and you already replied... I'm still talking about stuff from a half hour ago... \o/