I'm in the process of building a small mash tun out of a 2 gallon cooler for partial mash brews. It's pretty much one copper tube running across the middle of the cylindrical cooler, and I was wondering if I could get any input on the manifold. Since it is relatively small, I was thinking about drilling holes in it instead of using a hacksaw to make slots. My main concern is whether or not I should drill holes all the way around, or only put them on the upper surface. Anyone have any input?