Britbrat, you are right, but one advantage I find by using the 11x4 it that it limits top speed. And that lessens the chance of folding your wing, when making too hard of a turn. But on the down side, for someone learning, it makes it a little too easy to get out of sticky situations from too low airspeed, and being able to power out of almost any flat stall, with very little altitude to spare.