NOSRAM,

I finally got fed up enough with the tank & siphoning issue after flying the UCD today that I finally moved the tank. I really didn't want to spend the money for a Cline regulator so I had no choice but to make modifications in order to lower the tank. Actually, it turned out to be no big deal and I wish I had done this from the start. The air flow and exhaust channel underneath the fuse right behind the firewall is 1/16th (maybe 3/32nd?) plywood. This plate is simple to remove and exposes the entire tank area. There is one former that needs to be cut some and the side walls of the channel need to be removed. I then glued some new homemade formers at a level in the fuse that also created a ceiling (floor when inverted) at the correct height for the fuel tank. This causes the tank to be much lower than the original location and basically, locates it where the air channel used to be. I then inserted the tank and made a screw down hatch for the bottom of the fuse. This closes up the exposed area. I also epoxied a cover for the hole in the firewall where the tank in the old location exited through the firewall. I made a plywood plate for the lower part of the firewall area (in front of the new tank location) and drilled holes for the fuel line and vent tubing to exit forward. Now the tank is perfectly matched to the inverted carburetor height and is easily accessible by a hatch. Finally, I enlarged to cut out area in the underneath section of the cowl to allow better air flow escape from the engine compartment. This opening is now about three times the area of the cowl's inlet opening but can't be seen when the plane is upright. No more siphon problems and a smoother running engine.