I have to try the hi-gluten when it gets here.
2 years ago I took my dough & pizza over to the best bakery in town (Atlanta) so I could talk to the head baker. Turns out this guy was the head baker at Zabar's in NYC for a while. His breads are awesome. He never uses baker's yeast, only his sourdough culture. But he said that he was sure that the lightness of patsy's dough was on account of a combination of the sourdough with the baker's yeast. That the baker's yeast is what makes it light.
Also, if you read the "classic sourdoughs" book from sourdo.com, he talks about how the yeast interacts with the gluten. The softer the dough, the easier it is for the yeast to get started. It's like blowing up a balloon. It's always hardest at first, then gets easier.
I'm noticiing that with the DLX mixer my dough is amazingly soft. It's like twice as soft using bread flour as it was using AP flour and mixing with a Kitchen Aid mixer. So that, combined with all the stuff he says in the book, leads me to believe that mixing is a more critical than the gluten. Plus my own recent experienes. Not only is the DLX softer, but that softness is allowing the yeast to puff it up much more and the overall result is an order of magnitude lighter when it comes out of the oven.
How are you guys mixing? I've gotta say you should consider the DLX. It took a while to get used to but it makes 2-4 x as much dough as the Kitchen Aid, with far less effort and the dough is just much, much better.
Also, if you don't want to go that far yet (it's $450), then try my method of adding ingredients slowly to a battery dough using whatever mixer you have and include all the rest periods I recommend, and let us know if you see a difference, even using the same flour you used before.