Sweet. Thanks for the info. I was planning on rooting all the Rootstock tops with that same thought in mind.
I officially named this for you. "Dr. Delerium's Triple Play" TM (patent pending)
I get royalties on name use when you sell the concept to Bonnie's and they start appearing at every Home Depot...
From a plant physiological perspective it really should not work. You have 3 plants with different cambium layers merged into one plant and then mounted on another. I guess it is a partial cambium match on all 3? I hope I get a few to take as I really want to to do a cross section at the end of the season right on the graft area and see what it looks like.
You will have the opportunity to do it first, so do it when the time comes and post some pictures.
You already proved the petiole graft works and that probably should not have either!
By the way, have you had any fruitset and or tomatoes off the P. grafts?