I believe I have the SL-BS50-8 bar ends, the rubber is missing but the rest checks out. I think. They don't look like the Ultegras or have the same amount of travel. My question is this: Can I do the old 8-of-9 cogs trick with a non-DuraAce Shimano-indexed RD on a 7 speed hub? I did the math and it comes out to a 0.26mm wider cassette than the 7 speed, the lockring should take that up. Any experience doing the same with these goofy POSs? All my research says yes, but I thought I'd bounce it off you because you're smart and good looking.

The short answer is no. If want it indexed that is. IMO just buy a set of used 9 speed barcons on eBay and go from there. Good luck it sounds like a fun project.

Actually it probably can be done as an 8 of 9 on 7 setup, with indexing, if you "hubbub" the rear derailleur cable mounting position. That mounting should bring the cable pull down to about 4.35mm which should work with a shortened 9s cassette. That said, I have found the 8s bar ends to be a little off in general with their indexing so the best thing to say is maybe.