Our club has used Velcro to attach curtains to cover layout legs with great succes for many years.
The backscenes on our layouts have always been permanently attched with screws, in one case of a small folding layout, temporarily attached only as the backscene had to be removed to allow the layout to fold.
We aquired one portable oval layout with 10 boards where the backscenes were formed of 1/8" (3mm) masonite panels which were unframed. The layout boards were each 4 feet long and had 3" x !/2" (75 x 12 mm) frames flush with the edges.
We attached the backscenes with large paper clips. These are the type intended for large bundles or pads of paper where the clip is formed of blackened spring steel sheet, U shaped and operated by two wire handles which can hinge up to open the clips or the opposite way to lie flush, out of the way. Two of these clips per board gave a very secure attachment and spare ones came in very handy for emergency attachment of all sorts of things. They also had the benefit of being quick to use and requiring no tools.
My concern about using Velcro for this purpose is that in our experience, operators tend to lean against the top of backscenes and by so doing may lever a backscene board off Velcro fastenings.
Alex. W. Stirrat