David Wren got back to me.
Hi David ... sorry for the slow response. Regarding deflection "tuning" ... to tell you the truth, I gave up on using this technique because of lack of consistent results. It worked in a general sense when thicknessing a batch of different top woods and then testing cross grain deflection and long grain deflection (basically to quantify stiffness and then use the less stiff woods for smaller guitars) ... but for testing strutted tops (as in this photo) the results were ultimately too inconclusive.
As for weights and deflection numbers ... the big metal block is just my fret-buck (the block I hold under the fingerboard extension when I'm hammering in the frets) and is heavy enough that my little digital scale won't register it. I started using two weights ... a lighter one to just make sure the top registered on the supports properly (ie if the top was slightly twisted, this initial weight would get things sitting properly ... then the heavier fret-buck to deflect the top.
If you want to up your game, maybe start tracking the main resonant frequencies on your instruments. A free program by the name of "Audacity" is the simplest way to do this. Here's a brief video I made for a friend on how to use Audacity for tracking the resonant frequencies
https://youtu.be/gxb4guV6lPs
Trevor Gore's books are good for diving into the physics of the guitar ... they're worth it just for the summaries at the end of each chapter.
Hope this helps.
David Wren
