I use silicone caulk thinned with mineral spirits to seal the leather, and the silicone treatment makes gluing the gusset leather to the cheek board unnecessary. If the leather is not airtight after one silicone treatment, I repeat it. The leather is 4 ounce chrome tanned cow hide with a pigment finish. My gusset pattern is 11 inches at the widest point, and 5 inches at the narrowest point. The leather shrinks about 10% after the silicone treatment. The cheeks are 11 inches in length, six inches at the widest, and 3 inches at the narrowest. I plane the cheek lumber to 5/8 thickness. Pilot holes drilled in the cheek board ensure that the tacks will be evenly spaced. I buy the lumber, wood, and tacks on eBay. Although silicone works fine in bellows-blown pipes, using silicone to seal bags for mouth-blown bagpipes causes problems because a waterproof bag will retain moisture from the breath.