Loved the videos. Thanks, Prism.
I am going to try the styrofoam idea. Looking at my setup, there is a trough of about a foot next to the extension table on the left and then the other table, running parallel against it, starts. This gives me a luxurious surface after the quilt slides off the table in back, but not so much in front or on the side. The tables are adjustable but not quite at the same height, due the best height for each chair. I am going to wedge a few books in there first to see and also try a small pillow in my lap to get the quilt to start up higher.
Thanks to all of you who are helping me think this through. I tried to be analytical but was probably too close to the problem (literally) to see it.
hugs,
Charlotte