[QUOTE=WayneC1;20546741]GoldenTaco, the Shindengen really is the best option at this time for the 650GS, it is still a shunt regulator but faster acting and with less internal power consumption and hence less heat than a stock VR because of the FET components
If the worry about overheating the poorly design BMW stator is the main concern, I would point out that a shunt regulator that has "less internal power consumption" in other words for forward drop losses across the switching device (likely FET) is NOT what you want.
Why? Less drop/losses means that the total circuit series resistance is lower, this allows more current to flow thru the stator , causing MORE heating not less.
changing the regulator to one the limit total current to less than stock (400w) could help mitigate the problem of BMW's poor design....but at the expense of less out put for accessories.
Yes I too thing that useing a field regulating alternatore would be better, it would have less heating in generation, have lower loads on the engine..ie better gas milage....but it is more complex, expensive and likely heavier.
BMW has chosen the cheap simple approach but dropped the ball on stator cooling design.