Advice for a new Oracle Delphi Owner

You will destroy the belt if you don't turn the motor off at a change.
Look at the Oracle-audio.com site for instructions- the later instructions (Mk IV and up ) are better (just ignore the MVSS part). The Mk III can be updated to later versions when you get ready. Try to get the most recent belt and bearing available for the Mk III as an update. You can also get a later mat to replace the groove isolator mat, but if it weighs more, you will have to re-balance the suspension and perhaps replace the springs (don't go there). You might try to contact Herbie to find a mat at the exact diameter (with a satisfaction guarantee). Also get a washer from him to replace the original tapered washer. Always use the clamp. Do not replace it with a heavier clamp.
Happy listening!

I replaced the original mat on my Mk I Delphi with a mat like the one on the Goldmund many years ago. The sound was better IMHO, but it was a heavier mat,  for which I was able to correct the suspension by changing the springs.  I now have a Mk V with the new type mat (I don't think Oracle made a mistake). I suggested the Herbies mat and washer as a trial because it has a satisfaction guarantee, I have not used one personally. The original mat should be cleansed periodically with dish soap and water.
 Changing the height of the towers also affects where the belt rides on the inner rim.  if you get it too high, the belt will not stay on the rim. On my MK V the height of the skirt above the base is 18 mm with a record and clamp on the platter. i just checked and it bounced about 25 times.
If the Mk III has the newer style 2-piece bearing, contact Oracle to see if you can update the bearing bottom for the one on the MK VI with a polymer thrust pad. It is a big improvement. Also get a new belt and bearing oil.

From your response I would say you have the older bearing.
The barrel of the newer bearing in in 2 pieces separated by an o-ring.