Dear Mr. Krall,  There are several ways to go about rebuilding your
Welte primary valves; I have restored several.

To change the fine leather in the primary parts, if it's really
important, you can cut the chest with a very fine saw and then replace
the wood, but make sure beforehand that the original position cannot
be changed.  [Maybe install guide pins.  -- Robbie]  There could be a
possibility to open the glue joints with the help of a microwave oven,
someone told me; I have never tried this.

In some cases I installed a new valve system, like the later Welte
models used.  The later model is a much better system for reading the
rolls.  No matter what people say, the later Welte plays better -- the
models from the nineteen-twenties.

But then it's a question if you do a restoration like the original one
or you try to have it playing better.  Much of the pianissimo playing
wasn't very precise on the older Welte, you can hear it.

Best regards from Paris,
Douglas Heffer