I started a thread not long ago that described my attempt to flatten a 7’ by 3’ walnut tabletop with using the methods (to the best of my understanding) the Schwartz describes in a few places. I started with rough boards. You can look at the responses I got, mostly that it was too much work or that it wouldn’t work the way I hoped. I stuck with it. Now I’m not the greatest woodworker in the world and have severe physical limitations. I was surprised at just how easy it was and am thrilled with the results. You can judge for yourself.