About 2 years ago, or some thing like that. I posted an idea that may help this Ballast Thing regarding home builds. It?s dirt simple and cures a few problems. The idea: Two tubes with a slot cut in them from one end to the other. A tube on either side of the sub. When you want to reduce ballast you just turn the tube and let out some air. When you want to go back up,,,you just rotate the tube so that the slot is back down a little bit, and add some air. But the tubs create an automatic and infinitely Variable ballast system. It?s also very easy to build. There are several ways to put the air inside and to rotate the tubes and your imaginations can come up with good ones. But the concept is a good one and would work. And if one sets the tube so that the slots are at a cretin point in rotation then that becomes the variable ballast. It also eliminates valves to let out air for the ballast system to operate. Things happen very slow down there and if one is traveling at even one knot the speed seems to be about right. At 3 knots one starts looking for the break pedal. DJB