I used to take triumph/bsa lower legs off the bike before removing tube from tree. I am going to put spring and spacer back in tube and recap it, and try to remove bottom allen bolt with the tension on inner parts. Will advise if it works. I have already removed fork tubes from bike and drained the oil, before I realized you needed RYCA tool to reach inside and hold valve while removing bottom allen bolt. I do think I saw somewhere  someone described a way to make a tool that worked.