I take it from the context here that the motherboard stays powered alive if a battery is left in a Pismo eh?

That sucks... been there too. I fried my only IIGS motherboard back in the day when live pulling and reseating a TransWarpGS... I could have sworn that power supply light was out! Thank goodness it was only the motherboard at 349.00 swap that died and not the 499.00 TWGS at the time.