Detlof: I routed the aluminum plates, just two routes per plate. They are about 3/8" wide and almost as long as the plate, stopping about 1 inch from either end (long being side to side in this case--if that makes sense). Then you have one with the grooves on the top, put two marbles near the ends of each groove, then put the other aluminum plate with grooves downward onto the four marbles. That's my recipe for my aluminum marble sandwitch. As to the concerns of heat dissappation--these concerns are probably correct for tubes or other types of amplifiers which do not have the heat sinks located to the outsides as mine do. Also, the ambiant tempurature and air flow around the units play a significant role. My units are only about 2" separated, which is adequate, although I have been considering increasing the flow under the bottom amplifier. In this situation it's really how much airflow you can get around the heat sinks--how much heat dissapation per hour. With tubes, this is probably much more difficult to accomplish since the heat generating device is located centrally in the amplifier--rather than on the external sides with massive heat sinks. I should have considered this with my original post.
