One source for rebuilding the glued Gulbransen stack is the book by
Arthur Reblitz, "Player Piano Servicing and Rebuilding."  This book
talks about two ways to remove the tiers from the main vacuum board.

One way is to saw the vacuum chamber into three separate pieces.  The
other way is to remove the screws holding down all the tiers and use a
hard wooden block to knock off each of the key pneumatics.  All of this
pounding also loosens the glued tiers from the main vacuum chamber.  I
haven't tried freezing the parts to help make the glue brittle, but it
might work.  I have not used the saw method for separating the three
tiers.

Do not saw the key pneumatics off of the three tier boards.  You need
to reuse these if at all possible.  Even taking off 1/32 of an inch is
way too much.  You will have to break each one off using a wood block
and mallet.  Label each part as you remove them since you will be
gluing them back to their original position.

I don't agree with using leather seals to reattach the key pneumatics.
Just use hide glue to attach the key pneumatics to the tiers.

You will be doing something different for connecting the three tiers
to the main vacuum chamber.  You will make new leather seals and glue
them to the main chamber.  The three tiers are then mounted to the main
vacuum chamber with screws.  Do not glue these as done in the original.
This helps with the next rebuild process

Pete Knobloch (Tempe Arizona, USA)