What an odd theme, based solely on the syllabic length of the clues. Very strange. We got it from FOURSYLLABLES (57A: The theme, part 3), and then were able to fill in the first two parts, but still... I'm not terribly wowed by the whole thing.
Furthermore, LOANERCAR (6D: Wheels for a while) would probably have been better as "rental car," and "19A: What walls might hide" (SAFES), should probably have been "What pictures might hide," but it would have been too many syllables. And "23A: It may be felt" (TEXTILES) seems a little weak, too. And LIFEBELTS? OK, whatever.
I don't know, maybe it's just me, but if I had to sum it up in four syllables, they might be "Not a fun solve."