Hi Scott,
I don't know about the boom location, but can offer some insight on the sail changes. I have a 1995 Hobie 20, and the Skip Elliot sails are MUCH fuller than the current cut. I had my SE main recut by Calvert, and it had roughly 9" of luff curve built in, and when they were done, it had 4 or 5. The current sails I believe are also in the 4 to 5 range.
I also just purchased a very lightly used 1998 main, and I love it! Rumored to be quite similar to the current cut.
The other item of interest that I've noted on old vs new, is that the old sails had a shorter luff. I laid my SE main on top of a new main, and found the luff in the new main to be at least 3 inches longer than the SE main.
There have been several changes since 1992. The ones I can think about off the top of my head:
1. Different rotation system. I believe they've gone to Nacra style, but it definitely is not what you have.
2. Boards held up using side loaded bungee system, instead of shimming the trunk.
3. Tramp pocket added. Your barber hauler wire is exposed. 1995 and newer have a pocket that covers the wire.
4. Carbon blocks? I think they may have gone to carbon blocks on the mainsheet, but am not sure.
5. Hull rumored to be more durable. I think they may have added some bulkheads, or they're glassing them in better now than in 1992.
Other changes, I don't know, but perhaps someone else will chime in!
Good luck,
Tim J.