Based on a group email from Dan Weseman, I tried connecting my RDAC rev counter input to the non-regulated side of the alternator. By setting pulses to 12 or 12.5, I was able to get readings that were correct in the low range, but which did not track as I advanced the throttle. I spent the rest of my time trying to position and test a hall effect sensor from MGL designed for use on the Jabiru. I got no readings at all. Back to the drawing board.