Oilmanmojo , I have been reading your Apollo adventure with great interest. I have a few suggestions for your consideration ; in no particular order :
1. Clean the air manifold: Removing the manifold and cleaning the airbearing with a oil removing solution does wonders for air flow and arm stabitily.Clean the plith while your at it.
2. Do not underestimate the effect of filling the spindle tube with a "light" dampter. I used a Home Depot product that is sold to fill open spaces around windows. Very easy to apply & interms of dampting scores a 3-4 out out of 10 , an excellent way to improve the spindle w/o excessive dampting & weight.
3. Before re-assembly,lightly spray & polish parts, such as, the spindle, air manifold's inside air bearing ; the inside of top / bottom air bearing plates with Eagle 1 Spray Detailer ; its available almost anywhere auto parts are sold. The result has to be experienced to be believed: All air bearing parts operate so quitely , arm stability is improved.
4. A light damping the bottom of air bearing plate's underside & replacing worn or hardened rubber , returns the pliths performace to like-new or better. You are also assured the bottom bearing is flat ,secure & will not excessively "ring". I feel the top plate must revolve on a "lightly" dampened lower plate to bring out that last breath of air in certian recordings. "Light" is all you need. Again, this has to be experienced to appreciate the difference.
5. Test the platter & air bearing plates for "trueness" before going any further with truing/sanding the platter to assure neither is so out of round the repair may be out of reach.
6. When replacing the center pin use a soft wooden dowel to push the old pin. Then, gently tap in the new pin to seat slightly higher than where the former pin rested. Next, put the top plate into the new center pin , gently push down,by hand, onto the top plate to "seat" the center pin. I have learned that my failure to seat the center pin as outlined can result in "air swoosh". Only that gentle push by hand seats the pin.
Wishing you grest sucess.