During an outside loop, the fuel level moves around and relocates just like during inverted flight respect to the carb's height.

I believe that the engine cannot just hold more than few seconds at idle while inverted, when the muffler pressure is minimum.

If the centerline of the tank is too far from the needle height in normal position, the carb feels a dramatic change in fuel level when inverted.

If that is your case, and relocating the height of the tank is not practical, a compromise in tuning the low end between upside down and right side up may be a solution.