I am sorry I can't answer your ? on size, however I have a story about my college bed quilt which may give you an idea.
I received a simple patchwork quilt made out of blue jeans when I went off to college. The maker included pockets on some of her blocks. The backing was red denim. That quilt is still with me today 35 years later. It was used by my 3 children growing up and brought to ball games, picnics etc. It still looks great! You may already have your fabrics or theme but I thought I would share. Have fun!