...and after Autumn comes Winter. Now I know the process I was able to mount up my Winter piece too. This time I used a deep purple velvet; a charity shop find for 50p for a long strip.
In the interests of spontaneity I did what Burn kept telling me and didn't measure anything, just tried to get it the same size as the last panel by eye. Hmmm well, it's about an inch smaller so I am going to have to live with that if they are going to hang together on the wall. I might measure the next one!