Ron, I am not sure if it will improve the setup but it will create a solid connection between the bridge and spider. I can't seem to find any mention of someone else trying it, so it is either new or just over kill.
When fitting a piano pinblock to the plate you must have solid contact between the two or tuning stability is effected by the possible movement created by the almost 20 ton stress of the strings at concert pitch. With the contrasting materials of cast iron and wood, it is extremely labor intensive to make a void free surface on both. To solve this, rebuilders use marine epoxy to fill the gaps. Place wax paper in the spider bridge slot and then insert a small amount of the epoxy, enough to fill any gaps in a rough surface, and then press in the bridge insert. Once dry you will have complete void free contact between the two.
However, in piano work the epoxy has only to fill the gaps and does not transfer string energy. With a resonator it will be part of the energy transfer process and I do not know how it will effect that. I realize that purchasing a higher grade spider or using the Schoonover modular unit may make this unnecessary, but if you have a spider that has casting issues this might be a solution. I do not know how long it would take to mill a better slot if the equipment was available, but I do know this process is relatively straight forward and requires minimal equipment needs. It could even eliminate the need for concerns over a bridge insert that was slopping fitting.
I was just pondering the possibilities of a process transfer from one building technique to another. It may really only be academic and not practical but thanks for asking. I try not to be a geek but my academic side comes out sometimes.
Besides, someone may have tried it already and the ignorance of my inexperience may be showing
