The latest.... On the way home after 20 minutes on the freeway, "blinky" turned orange at 5,000 RPM. I have the Roadstercycle indicator. In my setup, this equates to about 13.2V output at the R/R. Then I assume the fan came on, battery voltage dropped to about 12.6V-- all of this at 5,000 RPM. In the two miles off of the freeway, I never got over 12.6V. I grabbed the multimeter and checked things out-
Stator all good- 1.0 ohms, 35V at 1500 RPM, no leg-leg shorts or leg to ground shorts.
I have not relocated the R/R and it was HOT, about 150 degrees F or so.
I thought there was a problem with the R/R checks (doing it by memory), but in the time it took to print out the checklist and re-check, everything was fine. R/R was cooling off by now. I plugged everything back in and started it up. Was getting 13.2 at idle. Fan came on while the R/R was still relatively cool, was getting 12.9V at idle, which dropped in a linear fashion over time (as the R/R heated up.)
It looks like perhaps the MOSFET does not like the stock location because it is too hot (duh.) I did not expect that 150F would affect it, perhaps it does. It is also possible that the R/R is generating its own excessive heat in some kind of failure mode I haven't been able to spot yet. In any event, my issue seems to be with the MOSFET, the mounting location, or both.