Found parking brake, also found the owners and service manuals on the Toro website, was surprised they were still available.
https://www.toro.com/en/parts/partdetails?id=28191
Didn't make a difference, but on or off seems smoother at at the governed WOT.
Could be fine and me being used to a twin.
Do these models not have a park brake?
Thanks Ken
Didn't get the chance as hoped, will try again tomorrow and report. Did look at the PTO and felt it but it does not seem to have but a little vibration, very little actually which surprised me.