Hi Ray,
Sorry to hear you are still having a loose grease problem but it appears you are getting some good suggestions. When I had the same problem, Tom Hughes suggested that I make sure the bolts were uniformly tightened and that did the trick. In addition, Frank Catt said that the CVs might have been packed with too much grease. But I could never find out for sure how much grease is the correct amount. Also, on my ZF trans, the CV and ZF mating surfaces are both just flat metal with no gasket or o-ring. Perhaps you could those surfaces to see if they are really flat and smooth. The attached picture is a close up of the mating side of the CV with a Plexiglas plate temporally bolted on to hold it all together and keep it clean.
Another small detail to check is to make sure your bolts are all the correct length and are all matched. On my car I noticed that 2 of the CV bolts were shorter and lighter which cannot be good for a rotating mass. I replaced all the bolts with high strength units that were matched (equal length, equal weight, drilled, and safety wired).
Bob