Great question. I too have a similar issue, although I feel under most temperatures, both settings are too hot. I was on a trip last week and the temps got down to around 0 C and I was wearing my summer gloves (big mistake). Even on the lower heat setting, my palms were burning and the backs of my hands were freezing. The backs of my hands being cold is my own issue for having the wrong gloves. But I kept having to pull my hands off the grips and hold them out in the wind to cool off.
I would love to find a fix to regulate the grip temperature. If the GS911 isn't the answer, I'm going to have to look into adding in a voltage reducer (amp reducer maybe?) in to the power wire heading to the grips. I'm no electrician, anyone know the best method for this barring GS911 success?