Yes Piers, I think you hit the nail on the head. Perhaps I thought that if someone recognised that it was made by "such-and-such" (without me giving away too many clues), then that would be reassuring. I also thought it would be reassuring to hear that some of the experts thought it was a quality piece. So far, all of your responses have been very reassuring. I also apologize because, secretly, I realize that I may be trying to show off a bit too.
All sorts of crazy insecure thoughts can occur in the middle of the night. Like: What if it's not genuine? Did I get my moneys worth (is it a quality piece)? I have no reason not to trust the experience and the judgment of the vendor, but I have little experience judging swords and I do not know of anyone locally (with experience) to whom I can show it. The guy I bought it from will think I'm certifiable.
Recently one of my friends discovered that an expensive painting which he bought from a reputable Canadian gallery was a fake. It wasn't discovered until he showed a picture of it to another experienced dealer. Fortunately, he got his money back.
I have no reason to think that this sword is a fake. To my inexperienced eye, it looks like a beautifully made sword (albeit with a few small flaws) that is likely as old as the attribution suggests. The nakago is shortened and there is no signature. The papers appear to be genuine. When I said "flimsy", that was just a figure of speech.
Thanks again for all your replies. The NBTHK papers say that it is a Yoshioka Ichimonji.
Peter F