Doweled the screw holes and waiting for glue to dry:
While the plugs are drying, I figured I'd work on #3 because the neck was just slightly mis-aligned. In typical SX fashion, the screws are drilled and set crooked.
Since I liked what threaded inserts did to the tone, I went ahead and installed them on #3 as well. Because the holes were crooked, drilling the neck was exciting again, but a light touch on the drill let me "feel" where the original hole was and follow it pretty well. Everything seemed to go smoother on this one since I knew what I was doing.
Shimmed this neck pocket as well while I'm in there. Notice how the pickguard is not fit very well on this bass, and there's a gap on the long side. More "custom handmade" goodness. Gotta keep in mind that at this price point, some soap in expected, and it doesn't effect function or tone.
With this setup, I was able to adjust the neck to the proper position and then crank it down. . . here's how the flat head stainless screws look on the back side. Not the prettiest, but not bad. I feel the screw heads could be bigger and oval heads would look better, but these are perfectly serviceable. The screw holes being crooked doesn't help the look, but it's in.