CD, I like what your came up with as a MUTT. I like that you have taken some of the weight off the treadles.
My favorite treadle belt is the aquarium tubing. Using a small 1" piece for the adapter works well and is quick for assembling. I have found that this is the fastest method for setting up any treadle belt, since no sewing or metal clip is needed.
Thanks for sharing info and photos!