Can't add much to that, Rio, you about covered it. I started building boxes for much the same reason. I wanted to experiment more with native woods, and mass produced calls just don't offer that variety. And to buy custom calls of those woods was cost prohibitive.

You said that the the screw should be turned about 1/8 turn, or no more than 1/8 turn and I agree with you on that. I would also add that when you get close to the sound you want, a minute adjustment can make a lot of difference.

Also, one trick that I have picked up is that on a box that wants to squeal no matter what you do to it, try rosin. You can get it in a sports store or music shop. Baseball pitchers ust it for a better grip and violinists use it on their bows. Just be careful with your call and don't let it get hot. The rosin will melt at somewhere over about 90 degrees F .