Upright Frame/Rim Integrity

[Farrell]

Rebuilding 1913 Mason & Hamlin 54" upright. Have soundboard out. This piano has a spruce (I think) frame (not sure yet what wood the top and bottom side-to-side pieces are) upon which a rectangular hard maple frame is mounted with two cut-off bars, and the soundboard sets atop the frame. The pinblock is glued to wood that runs above the soundboard which in turn is secured to the back posts.

My goal is to make this piano at least as good as new, and hopefully better than new. If the sides, etc. of this piano had just about fallen off like some uprights I have taken apart, I would be well aware that there would be cause for concern about the integrity of the frame/rim/pinblock assembly. This piano appears to be pretty sound. But of course, I want it to be perfectly sound. 

What methods are available to us to evaluate the integrity of the frame/rim/pinblock assembly on a piano like this. The only thing I can really think of is to start picking away at it with a chisel to see if anything is loose, but this obviously opens up the door to damaging something that was good to start with. 

Should I put on a new pinblock regardless (I think so)? (Old one could be plugged.) Should I remove maple rim and reglue just to be sure? Should I epoxy in big hard maple dowels in all the frame joints just to be sure?

Any good ideas? Am I the only one ever concerned about this? Thanks for any thoughts.

Terry Farrell