Interesting way of measuring the difference in aoa. I appreciate you sharing it and also your various other posts of methods of tinkering with foils.
There is no doubt some foil theory about all this but I haven’t looked into it.
What I do know is that I put a reasonably chunky washer under the rear bolt and rode it around for a while. This was so I could move my rear foot back without opening my stance too much. Initially I liked it and thought it was better, but then came to a realisation sometime later that it actually rode horribly, especially with speed and even appeared to nose dive at higher speed. Clearly way too much change in angle. Without shims rode much better. Your very thin butter lid shims though make more sense so I will try one or two of them out and see if feels right