Just had a look in my Herbert 0V operators manual, no help. I made a new spindle with a 4MT taper to suit some existing tooling I had. With hindsight I may have gone for a small international taper. Would the OP consider this approach? Not 4MT but 5C or R8?
I have collet chucks for the machine but prefer to use collets that fit directly in to the spindle nose, far more rigid then a chuck protruding from the spindle nose. Also more Z axis capacity.
My 4MT collets are ex-Meriden Triumph tool room.
The 0V is a nice machine, very rigid and accurate, I'm surprised more haven't found their way in to home workshops.
NDIY, can't find the thread you mention, got a link?
John.