I am not familiar with the Cremona but I have done this repair on
several upright players of different varieties.  I use 3/8-inch
carriage head bolts with the nuts on the plate side.  I clean out as
much of the debris that has gotten in the crack as I can without making
more or driving what is there in deeper.  I then put pipe clamps next
to each lag bolt, screw, etc., that is supposed to be holding the top
end together and just tighten the clamps up snug.

Next I remove the screws, lag bolts, etc. and, if I am going to use
an adhesive, I work as much as I can into the crack using a thin tool:
a pallet knife, cake frosting spatula, thin putty knife, feeler gauge
stock, or what ever works.  I like the West System Epoxy with some
colloidal silica for thickening for an adhesive.

I then tighten the clamps to draw the crack as far closed as possible.
There should be significant adhesive squeeze out.  Then I drill the
holes all the way through and put in the bolts and tighten them up.
If I can I like to position the bolts so that there is one through each
back post.  If it looks like it will help I may put on more clamps.
Leave the clamps on until the glue is cured.

On a piano with a 3/4 plate, like some Kimballs, I make a plate to
go across the front of the pin block above the tuning pins.  I use
something like 2-inch wide 3/8-inch thick steel and trim it where
necessary to fit above the tuning pins.

For a crack of an 1/8-inch or so I do not loosen the strings, but with
a crack of 1/2-inch or so I always loosen the strings.  Between these
it is a judgment call depending on how the piano feels.  If in doubt
I would loosen the strings.

If there is a problem with the pin block coming lose frequently there
is also a problem with the bottom of the piano.  The repair is
basically the same.  I would check it carefully.

I know of one show piano where the technician used hex head bolts with
the head on the inside and counter-bored the back to recess "T" nuts
about 1/2 inch.  He had the bolt heads chrome plated and when he was
done he put wood plugs in the recessed holes in the back and sanded
them off flush.  It made a very good looking job.

Most of the players I do they want it to play well enough so they can
have the neighbors over, have a few beers, and stand around and sing
off-key.  They don't care how the inside or back of the piano looks
as long as it plays.

John Dewey
Penfield, Illinois