I also am a fan of the JennOop suspenders. Two years ago I bought a Sweet 16 sit down with side extension table. I still had problems with balancing the weight of a large quilt, my shoulders ached (Maniac, I flip my quilt on mine LOL), and actually hated my machine to the point where I was going to sell it. I saw the original post here on QB and being the gadget lover that I am bought it. I love it!!! It is such a simple principle but there is no drag on large quilts, my stitches are so much more even, and I fell in love with my Sweet 16. Do I sound like a commercial? Sorry, but I've seen such an improvement in my FMQ that I'd recommend it to anyone, my friend uses one on her DSM.
Yes, they would be easy to build but MrJanRn would say "I'll get around to it" and never would.