Hi All,  First, the U-bolts that hold the stack in place do not keep
the stack together.  On the bottom side of each end of the stack there
are two 3/8" nuts which are used to bring the tiers together.  Quite
often, these nuts are buried into the wood because the wood itself is
relatively soft.  To gain access to the nuts, it's often necessary to
remove the piece of metal that is connected to the bottom of the
U-bolts that hold the stack in place.

Second, regarding the testing of the cut-out, the easiest way to check
its function is to disconnect the trigger tube that is connected to the
device.  This eliminates the need to "force" anything, and it checks
the device 'at the source'.

I've had a number of experiences where the valve that's used to turn
the cut-out 'On' and 'Off' makes a poor seal.  When that happens, the
Cut-Out device will be partially closed, restricting the vacuum from
passing through to the stack.  (In essence, it becomes a choke-type
volume control.)

After the cut-out is tested, it's wise to then test the trigger tube
for correct operation.  If the valve that's activated by the movement
of the transmission linkage does not seal the trigger tube 100%, find
out where it's leaking.  In my experience, the problem is often found
to be the leather that is used to seal the trigger port.  And, in some
early models, the port was sealed by a piece of spring metal which
covered a sponge neoprene washer.  If the spring gets cocked to the
right or left, it will create a leak.

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA