Just relax, take it easy.
A few years ago, I gave a Fender Squire Stratocaster Junior to my son and an Epiphone LP Junior to my daughter. As it turned out, my daughter preferred the ukulele over the guitar. After awhile, she gave the Epi back to me in exchange for something else. At the time, I was not at all interested in spending any time playing an electric guitar. Fortunately, my son was already outgrowing his baby Strat, and he had grown enough in size and muscle strength to handle the Epi's longer scale length and relatively heavier body. After another horse trade, my son took possession of his second electric guitar.
After replacing the bridge, it was time for new strings. Considering that the strings on this axe had not been changed in years, I'm guessing a set of Ernie Ball Nickel Regular Slinky, 10-46 gauge, is what I had removed. Having a set of Dunlop 9's on hand meant it was time to try a relatively lighter set of Dunlop 9's on the Epi and see how she rocked and rolled.
I spent the next half hour or so trying to set up the Epi, and made two discoveries. First, I found out she has a one-way truss rod. This would not be a problem for some players on some guitars, but I could not get enough relief on the neck with such a low-tension set of strings. Second, I found that the new bridge had just a little more height than the stock bridge. So, I had taken a guitar that suffered from string buzz on some of the lower frets that also had terrible intonation and no way to adjust it, and made it into a guitar that could be intonated with high action.
At this point, a novice player with access to Allen wrenches could destroy a guitar neck quickly and easily, by over-torquing the truss rod in an attempt to adjust the neck angle. It's important to understand that a truss rod is something that can make neck curvature adjustments only, and only at the lower-frets of the neck. This adjustment, combined with the proper nut height, bridge height, fret crowning and neck set angle, can be made to produce desirable string action.
The only way to possibly make a set of 9's and the new bridge work on This Old Guitar was to change the neck set angle. By slightly angling the neck towards the back, I could use the bridge height adjustment to get the 12th fret action into the playable range. If the string buzz was still an issue after the neck settled, I could look into replacing the truss rod with a two-way model, but that would be even more work than installing a stop tailpiece and separate lower-profile bridge. More likely, if the neck set angle didn't solve the problem, I would just switch back to a set of Ernie Ball Nickel Regular Slinky, 10-46 gauge strings.
Noting the country of origin on the neck plate, I removed the plate and braced myself for some poor quality craftsmanship.
A tell-tale production fifth hole in the neck was the first thing that caught my eye. Not an issue, everything looked fine, so far...
It was nice to find that Epi actually made an attempt to adjust the neck angle with a spruce shim. Yet, it was an incomplete attempt. I recall that the guitar had some fret buzz in the first five or so frets from day one. Without a way to torque some relief into the neck, I now knew all too well why the frets buzzed. On the brighter side, the four neck bolts and their receiving holes in the body were in good shape.
Another quality problem is this poor finish job in the neck pocket. The finish is rough to the touch, leaving lots of gaps between the neck and body. There is also an area at the production hole that did not receive any paint at all. I decided it would be best to address all this with some sanding and clear coat, to help keep moisture from finding its way into the wood, after getting the set angle close.
To increase the neck angle, I made a new oak shim. From this picture, you can see that the new one, on the left, is about twice the thickness of the one on the right that had been installed at the factory.
With the new shim in place, I re-assembled the neck joint to try out the set angle. Although it played better, the angle needed to be brought back a touch more to get the bridge up slightly off of the lowest adjustment. It was getting late, so I decided to first see if how comfortable my son was with the feel and the slight buzz of the 9's. Ssanding and re-finishing the body side of the neck pocket could wait for another day, after deciding what gauge strings to go with on This Old Guitar.