the airholes depend on just how low in resistance your thinking on going. I would maybe start at 1/16 and go from there. 26g wire is a great wire and gives you some options. my personal preference is taking a 1/32 drill bit and wrapping around this. this gives you a very small coil which I then use in a dual coil set up. I like a total resistance of about .4. also I don't
thread the cotton thru the coil but place a bit under each coil. there are so many set ups so experimenting is the only way to find what you like.