There is a reason they are finned these days. It will depend on the power draw etc.. And it is backwards.. The more electricity used the less heat the R/R will make. Because the way the R/R works is it turns excess unused power generated by the stator into heat. (so high beams on headlight will have the R/R create less heat etc.)

 

ok thanks guys!
my old one had cracks in the plastic part and it looks like the crap inside it puked out.

 

I drilled many small holes on the undeside of the side panel (are invisible unless you bend down to look) to enhance the cooling. That was over 50,000 km ago (when I installed the new vented unit) and all is well....