[airspirit]

You might want to try this, and making the water channel at the base wider than the channel at the inlet. This would force the water across the block faster and allow better thermal xfer. Otherwise you'll have faster water flow at the top of the channel and slower at the bottom at the die contact point. Good idea with the dremel, though don't go too crazy with it or you'll provide hidey holes for stagnant hot water. Simple scoring will do it well for you. I'd score the entire inside, though, to allow for maximum heat xfer at all points ... this has so little surface area and water surface area that it will definitely increase heat absorbtion rates.