Don, I've neither used your stretchrelief pliers or the manual Quickmate fixture that i reported on. They cost about the same, $250 for the pitbull type or $300 and change for the Quickmate.
On thing that seems cool about the quickmate, is that you can flip it over once the fixture has been installed, and check that the frame is correctly positioned on the stretcher bars, prior to installing any staples. If its out of alighnment, loosen and retighten.
I would like to buy either the pliers you recommend or the Quickmate, either would be an improvement over the simple Frederick pliers i have now. Does anyone see a fatal flaw with the Quickmate - looks like a pretty good deal.
One thing about the quickmate, a flaw perhaps or not, one can't apply lateral pressure on the canvas width while the first pull is across the longer direction. Yet apparently, it leaves a very tight canvas.
its a puzzle to me which might be better.