OEM Harmony Sovereign braces installed with early PVA glue (like Elmer's white glue) pop right out.
The PVA glue they used is not compatible with aged spruce. PVA glue requires a newly cleaned, scraped or sanded spruce surface. It appears Harmony did not do this. They probably had tops stacked and stickered for quite some time before the braces were glued. PVA does not like this. So, Harmony top braces are easy to remove.
When removing the glue residue we scrape, being careful not to remove any top wood. When the removal process is complete, you can always see a bit of the original glue line.
Also, in this image you can see the bracing we add to the sides. This remedies side wrinkles caused by string tension over the years. These are much loved forty and fifty year old guitars after all. Side distortion contributes to the characteristic top cave in. We pull the entire body flat (so the top is flat) then clamp the heck out of these braces so the sides are straight and true. This is one reason our guitars have a nice solid play feel. Play an original and one of our rebuilds. The difference is significant.