Be aware however that whereas normally such a "low voltage cutout" (LVCO - eg, MW728) ) device would itself be switching the load direct, in this mode, the LVCO is merely turning a relay on/off. (That relay controls power the load.)
Therefore the extra voltage dropping diodes etc see a more constant load - ie, the LVCO will its relay on on off (eg, 10mA sensing current with or without (say) 100mA for its relay) as opposed to a 10mA to 10A range with the end load connected.
It is that former load (say 100+10mA) that you select your diodes (or resistors) for. (But make sure hysteresis isn't a problem - if so, add a latching "off" mechanism.)
all of those points are in the design of my circuit. i just made this design because anyone can go to radioshack and buy all the parts needed. its fully and easily adjustable too, at any time.
ill look into that oatley kit though, it sounds like it might be worth the money.