I have just installed a 10oz rectangular fuel tank in my sig kadet mark II. The tank has a small bubble on the top for the vent tube to angle up to. When I install the tank it angles down a little bit because the bubble rubs on the support piece for the nose. I hesitate to notch out the support for fear that it will weaken. I was wondering if my tank angling slightly downward (10 degrees) in the back will make a big difference. Other options would be a 8oz tank or try and heat the 10oz tank and eliminate this bubble. I would appreciate any feedback .

hwflyer

Ten degrees from horizontal is fine. 45 degrees for example, can be a problem, because when you are inverted, the fuel will fall to the front of the tank and the clunk in the back of the tank will draw air and the motor will quit.
But 10 degrees will not be a problem. Theoretically, when you are down to your last ounce of fuel and you fly inverted you may cause the engine to quit. but you should not fly around inverted when your tank is nearly empty.
If you always fly right-side up, you can put the tank at any angle as long as the back of the tank is level or lower than the front.

Turn the stopper in the hole 180 degrees. Now the bubble is on the bottom. Problem solved.

GO FLY.not that big a deal

Any solution except heating the bubble is fine. Like the comment above, go fly!