Thanks, Michael. As a matter of fact I noticed the beginnings of the dimples this morning. One is quite distinct; the other is barely a wrinkle in the leather. Guess I sit more on one side.

Not that I will be needing it any time soon, but I was looking at the picture of the tensioning spanner. It looks like what is called a flare nut wrench here in the U.S., sort of a box end wrench with a space cut out. I assume that when the time comes I can just use one of those if I have the right size. Have you had to tension yours yet? How do you know when tensioning is needed? The instructions say "check tension", but they don't say what to look for.