The new plastic protectors seem so thin that I feel the leg can still hit the cabinet with a hard nudge. The plastic protectors that came on my Metallica machine were attached crooked so that when I put the legs on one of them cracked (my bad, but still....).
I changed them out to the metal protectors and then put the felt protectors between the metal ones and the legs. Overkill perhaps, but a permanent solution.
Scott