Forget clunks, forget all of that third line plumbing. Use the Tettra bubble-less tank. Jett engineering also makes a similar line.

This tank looks like a regular plastic tank with a bladder inside it. The bladder is the same size as the outer tank and cannot be stretched. There are two lines only. The feed line goes to the inside of the bladder. The pressure line goes to the fitting on the outside of the tank and pressure is exerted inside the tank on the outside of the bladder. There is no dirty burnt fuel going into the bladder.

To fill, the bladder is sucked empty with a syringe, fuel is then pushed into the bladder. You now have a solid bubble of fuel at the pickup. Because there is no air in the bladder you will not get a lean run, or bubbles in the line, even if there is some vibration. This tank solves all of the lean run, tank position, vibration bubble and needle setting problems. Whatever the needle is set at on the ground is pretty much what you will get in the air. The engine will not surge or gurgle, at the end of the tank it will just stop.

Ed S