The potential problem (no pun intended) I see with this is that the 650 generator is as we have discussed a fixed output device, said output dependent on engine speed and engine speed alone. So, as you reduce the "normal" system load (with LED lighting for instance) you are asking the regulator to dissipate more of the generator's surplus output.I'm converting to LEDs on the 650's power-hog lamps (brake/tail lights and turn signals) so I may try the Shindengen SH775 series regulator just out of curiosity. It's available from Polaris ATV dealers (part # 4012941).
Did I scare the O.P. off?
Series R/R is the way to go.Here are some test results comparing my old shunt SH-232 R/R to the series SH-775.
Disclaimer- I have no idea how accurate my ac current clamp meter is at frequencies above 60 Hz; I know it's accurate on 3 phase 60 Hz stuff. I suspect it might be pretty good at 120 Hz (1200 rpm), but at 400 Hz, who knows.
On the good old SH-232;
at 1200 rpm, stator line current = 6.5 amp ; R/R output 12.8 volts DC
at 4000 rpm, stator line current = 11 amp; R/R output 14.2 volts DC
On the SH-775
at 1200 rpm, stator line current = 6.7 amp; R/R output 13.0 volts DC
at 4000 rpm, stator line current = 6.8 amp; R/R output 14.2 volts DC
With the SH-775, turning off headlight, resulted in an immediate drop of stator line current to 3.5 amp at 1200 rpm.