Stepping back a few posts,
The completion alarm went off at 4.14v, my multimeter read 4.11, and my LF2XT is reading 4.26.
This doesn't seem all that unusual. Depending on what rate you charge cells at, the cell voltage will not be as high as the voltage of the charging circuit. Also, when the cell is removed from the charger, the cell's voltage will drop some. The faster the charge rate, the more the voltage will drop. Also, the older, or more used the cell, the more the voltage will drop.
As has been mentioned, the very best 10440 cells have a capacity of around 350mAh. The "600mAh" xxxxxFire cells are typically ~250mAh when new. So, either 100, or 200mA is an exceptable rate to charge most 10440 cells at. If you're in a hurry, a 300mA rate can be use with the better cells, however cycle life may be reduced a bit.
As for the LF2XT, you're lucky to have any voltage readout at all. It is unreasonable to expect such a light to have a $50 voltmeter built in. Still, the LiteFlux lights do give you something to go by, and when the cell voltage reading begins to drop rapidly, you know it's nearing time to change out the cell. Works well for me anyway.
I have no experience with 26650 cells, but looking at
these 4000mAh cells on
batteryspace, it appears that 1C is the maximum recommended charge rate. Again though, this may be at the cost of some cycle life. Personally, I charge all of my cells, NiMh, NiCd, LiCo, LiMn, and LiFe cells at 0.5 C. It's easy to remember, and saves some wear and tear over the maximum rate, for any cell chemistry.
Also, concerning Li-Ion cells (all chemistries), higher charge rates may not actually be all that much faster, in many cases. When using a charger that utilizes a proper charging algorithm, such as a hobby charger, the faster the charge rate used, the more time the CV stage takes. The reverse is also true, slower charge rates significantly shorten the CV stage. For example, I have never actually timed it, but it would seem that charging LiCo cells at a 0.5C rate, only takes about 20-25% longer than charging at a 1C rate.
Dave