Conrad, your OB's are much bigger than mine but you can probably tell when you are running in sync by the sound. If they are close but not in, you will get a thrumming sound, up, down, up, down. I have noticed on mine that the sound can diminish even if the tach RPMS are not at exactly the same level. Whenever the "thrumming" was gone, I figured they were in sync.
Harvey
SleepyC :moon