my collection of four 1300mah 3s lipos lend themselves very well to a 12s 500 maybe even a 550. The difficulty in making a 300 to 380 into twelve s is not the lipos since most any size, mah, and physical dimensions could make up a 12s lipo pack (I acquired a 350mah lipo yesterday to size up a small 12s pack for a 300 or 450) problem would be in making a motor small in size for the low kv requirements in that application.
One question I'd like to ask is when 2200mah 3s 11.1v equals 5 minute flight time, by dividing the mah x 4, will this be the equivalent in mah to give the same duration while cutting the amperage by 4 also? If this is true then only 25c lipos are needed in a 12s configuration.
Again, motor winding would be the only real problem to achieve proper kv in a small can.