For mass produced Tamboras, I recommend simply changing
the heads.
This JCR Tambora was made by Junior Tirado when he was
doing some of his work there.
I bought it 6 years ago from
a Chicago music store via eBay. The shell is oak. I used
some longer temporary lugs/bolts to make the mounting
easier.
Finally replaced the head this past weekend. It's a powerful yet
warm sounding instrument. A good tambora has a lot of volume and some
reverb overtones from the sound bouncing between the thick
and thinner sided head. The correct stick to use is much thicker
than a drumstick.
The thin side is traditionally goat, or sometimes two layers
of thin goat. The thicker side is cow. It took quite a few days
to dry.
Isaac