18650 LiFePO4 Cell UVP/OVP Under/Over Voltage Protection
UV- and OV-limits do vary due to LiFePO4 chemistries (yes there are quite remarkable differences). If not sure what limits you need try by charging/discharging at realistic temperatures and measuring the dU/Ah (steep at beginning an end of SOC).
Maybe you could make the (seiko) chips compatible with your (under)voltage level by adopting the measured voltage (between Vdd and Vss) so that the measured voltage is reduced ( that means protection level starts higher as needed with LFPs). Beware of changes of Idd and temperature dependent effects.