I only found this discussion,most similar to what's been wondered about here...
http://www.splintersandthreads.com/p.../NTN-HDD-Basic
In the piece she was working on in the you tube video, there was an awful lot of puckering around her own design(especially the long blue one with the daisies)...so I am wondering if she has gotten the alignment better but sacrificed the piece laying flat? I also noticed in some of her other videos, that she cuts out the embroidery, then appliques it to her quilts, so maybe in her case puckering doesn't matter.
I know that I wouldn't pay anyone 60 dollars for a piece of foam and some double stick tape, though! It might be worth experimenting with if you have an old hoop to play with.