great question, I use these cutoffs
Do note that unlike a li-ion pack, once these start going dead, they go dead very, very, very rapidly. (compare the mostly-horizontal {LiFePO4} versus mostly-diagonal {li-ion} lines on the two graphs above)
These aren’t li-ion packs. This is both good and bad. You get almost full power (not mushy sagginess) until it’s dead, but then it dies in an extreme hurry.
Stay above 31 for cutoff end. You can lower it a tad if you want. 34.5 / 33 seem to work really well though and I’d use that.