I post this to, maybe, help someone to avoid the anguish I've gone through. I was thinking about making the electrical upgrade to cure low rpm rough running and night driving vampire style when my battery went flat. It had boiled. Bad R/R I thought. Testing with polimeter showed well over 15.5V at 5000 rpm. Fortunately I have a crashed 87 Paso for spares so I swapped R/R. Things looked far better then...15.3V! F..k. After a day of head scraching and bad temper (curiously none noticed) and following several roads (the full length of the wiring harness) I found THE ANSWER.
Wiring harnesses as old as ours (I'm talking about the bikes here) pile up impedance with time, and as ours old Ducati R/R (bikes again) have a C wire going to them to tell them how the battery charge level is.....ergo. Voltage between + and - in batt 12.6. C wire shows 11.8. R/R thinks batt always low and overcharges.
Solution? Come o ... You know....another one! Other relay with wire from batt + to C connector in R/R triggered by C harness wire.
This went fine for me,but I'm no sparks man nor engineer. I fact I'm an Accidents and Emergency doctor. Thinking about it maybe the thing to be to deal with old Ducatis.
Hope this helps someone and sorry about the bad jokes. Thanks!

WOW ! that's amazing ! an A&E doctor that rides a motorcycle

Nobody lives forever. Besides there's a joke about it.

Doctor: You must follow my instructions really close. No heavy meals, quit smokinvg and booze, not going out to the pub, women just a little and then just yours, etc
Patient (with sad face): And following that points am I going to live more?
Doctor: Not sure,but your live will be way too long for you then