Hi Todd,

The best glue for the job is hot hide glue. The best material
for the job is cardboard, just like the original. However,
many makers used heavy bellows cloth for the inserts and you
will not be disappointed if you elect to use cloth. But it
must be heavy cloth, thin cloth will not do the job properly.

Musically,

John A. Tuttle (john@player-care.com)