Thanks Doug. 
Good reminder to check those isolator donuts.
I don't know if the different models use donuts with the same Shore value.
I’ve pondered removing the damper all together as Tracy ended up doing. See a copy of his email below:
I’d like a latter update with further info from Tracy. Not sure what year this was. Does anyone know?
Steve Izett
RD1-C on Renesis
Steve:  this is the first I’ve ever read about the no damper RD2/3 versions.  I wonder how many were sold before Tracy retired?  Since I have about 40 rubber dampers, I’ll just try and keep soldering on with my old school set up!  😎
Doug