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.