Thanks for the link, Mintyman. I have managed everything except for the unchecked letters in the unclued light at 20D. If I am right, the "distinctive feature" mentioned in the rubric means that *either* the first letter of 20D can be deduced unambiguously, *or* there could be 2 possibilities for the penultimate letter. However, all of these possibilities leave me with only five of the six letters of 20D and I cannot find a final letter which leads to any valid word which I can find. I have checked my answers to 22A, 25A, 28A and 34A and they all seem solid. Would some kind soul put me out of my misery?
Incidentally, did anyone else think that Doc was pushing it a bit with 24A?