Like the other posters have said eleven inchs is a long, long pull for a typical suction/muffler pressure system and there is no doubt in flight under various flight loads and attitude you will suffer leaning. As most have said the pump systems (Perry/varsane and Kline) are good solutions.

There is one other method that does work with less complexity/ cost that does work. No I am not talking about header tanks either.

For several years now bubbless fuel tanks have become the standard in pylon racing and it has become the norm to mount tanks centered on the CG. This can be at distances up to nine inchs depending on class. With a bubbless type no air or gas can be introduced to the inner fuel bladder and the muffler pressure is supplied between a hard outer shell (that look just like an ordinary tank) and the inner fuel bladder, there is nothing but fuel in the bladder. These airplanes are subjected to up to three time the 'G' load of an ordinary aerobatic airplane. when fuel delivery became a problem for these aircraft with conventional tanks the bubbless type was developed for them with results that are a miracle. Even though the actual pressure is the same as a standard setup the feed performance is far better.

Beside my pylon equipment I now occassionaly use this type tank when I have a sport plane with various feed problems.
They are available in sizes up to 16 oz. under the Tetra brand and sold by Central hobbies and cost about 14 to 16 dollars.

FWIW
John