I think this is the smallest you can buy and the canvas sits exactly flush with the back of the frame. Can I cut strips of 1/8" acid free foam and put them in that space to prevent the painting from wobbling back and forth in the frame? I guess I could put an entire piece of acid free foam core, but the painting is large. Can you "join" foam core backing with acid free tape? Or would it not hold. It seems strips would be easier. Then put dust paper over all?