Yea!! Plaudits to Dennis and IIS!!
I just made up one of these in thin paper from a scaled image in MS Word, with a sharp blade and a steel rule, and it works beautifully, looks like the image of Altair in Dennis' post. Great information
It is (accidentally, I did not really try) optimised for the Skywatcher f1000, being 3 + 3 = 6mm, and the electric focuser I just fitted to it helps a lot as well.
Cheers