I like the tube to transfer stress. I think it is a great solution to the problem.
I would put your SSQA implement on flat ground, with your adapter on it, and drive the PT over with the PT adapter plate on it. You can put a 4x4 or a 6x6 under the attachment edge of many implements to get an idea of the curl that you might need.
Some attachments like forks and buckets need quite a bit of curl toward the tractor on occasion. Other like augers need the reverse, the ability to get the plate (nearly) horizontal.
All the best,
Peter