I do something exactly like that but I use a rollable garment rack against my sewing table. It has the ability to be locked from lowest about 1 foot above sewing table up about two more feet. I do find myself adjusting it depending on the size of the quilt. Just like you I had bungee cords and rack already so it was 0 cost and it works for me. Those are pretty nice looking clamps you used. Would love to have some if I could justify the cost.