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I have the Tex Backup XML in both mini and long bodies (with a back up narrow coming). Runtime was a problem as the first burn only lasted 40m with the 3kmah 18650 cell.
Doing some reading about, the AW 18650 cells seem to be about the best choice and widely used. Not cheap at 20$ each. Charger is also important, and the Pila chargers have multi stage charging. I have one of those coming as well.