In my new plane, I was thinking of using 2 fuel dots. I got the idea from my recent experience with the Cline regulator. If I put a fourmost one way valve on the exhaust line, which would also be my vent line from the tank, when I fill, I would not get any fuel into the muffler. However one thing bothers me, the pressure buildup in the tank from the one way in the exhaust , is this going to cause any issues?

Have you ever seen how a plastic tank balloons with a Cline regulator installed? I would say any type of one way valve in the pressure line will cause some fuel delivery problems, most likely flooding.

No, I haven't. Hmm, any other suggestions since getting to the exhaust may be a problem with the cowl?

If the muffler is pointed down, just stop filling when you see fuel coming out.

You have 3 spots for fuel lines on most tanks. One to the carb. One to the Muffler, and one spare. Use the spare line as your extra vent. Set up the inside of the tank so the brass tube on the line to the muffler goes clear to the top of the tank. Then set up the extra line much the same way with the brass tube about 1/4 inch lower than the one to the muffler. Set up the fuel line to the carb as you normally would. Use a plug to cap off the extra vent line while in flight. Take out the plug to fill the tank. if set up correctly fuel will come out the extra vent just before the tank is full so you will not flood the muffler. I do this on my Boss hog because the muffler is up high. However if your muffler is at the bottom you can fill the tank till fuel comes out the muffler then just point the nose up before you start to get out the extra fuel if you need to. I can just start mine and the engine blows the fuel out of the muffler.