Rivendell says they haven't tried the Simplex retrofriction shifters on their bar end mounts, but that I can return them if they don't work. I have a feeling that they will because the retrofrictions were made at the time that standard brazed on shifter bosses became popular. I live near the Rivendell shop, so I may take some shifters down there and try them just to save on shipping. The first time I saw downtube shifters mounted as bar ends I thought it looked odd, but there's no reason why bar ends need to be short and stubby that I can think of.

If you haven't tried Simplex retrofrictions, you don't know what you're missing. Once you do, I'll bet you'll never go back.