Action Rail Shim height Mark I

[Skiroy]

So Thank Goodness I was able to find the keybed I needed with the keys. I was going swap out the hammer rail as they are both mid 74 Mark I. But mine had a shim added to the Action rail. I was told that this is set for the keys and keybed by Fender and I should abandon my hammer rail and take off all my hammers and dampers and swap them over to the new keybed with hammer rail(action rail).

The person that told me this is very knowledgeable and I dont not doubt his experience. I just would like know more about it as this is a big job that I did not want to take on. Im worried about the hammers and dampers having to be aligned due to the fact that they are individual dampers. The hammers and dampers have glue which tells me they may move over time so I would rather not disturb this.

But how critical is the action rail height and how does it effect the piano? Is there a a measurement or something to look for to make sure this height is correct if I just swap out my current action and hammer rail?

[Ben Bove]

It's not an exact science on these models, they tried to make it more of an exact science with the aluminum action rail.  So the best thing to do really on these wood action models that may use shims, is to experiment with different placements and see how it feels on the playing side.