http://www.thimblelady.com/copy-of-quilting-hoop/
If I've done it correctly, here is the link (I think). I have a similar hoop/stand combo that sits on the floor, holding the hooped quilt over your knees. I think this one you've mentioned is designed for you to sit on the "T" part?
Interesting design.... sorry I can't speak to how effective it is.