Surely, the loop has got to look round from the Judge's point of view ? So, it isn't actually round, just seems so. And probably explains one reason (among many) why my loops don't look good.

Think of the geometry of the situation: you fly a perfect circle vertically above the ground, but the judge is looking along the axis of a sort of cone at an angle to the ground. Consequently he/she sees a sort of ellipse which will be flatter than a circle. But if you fly the right ellipse (taller than a circle) it could appear as a circle. If we know some measurements we can calculate how different the circle and the ellipse are.

Quick calculation (back of envelope) suggests that if you fly a vertical figure 150m out from the judge, who is looking at a base 15deg above horizon and a top 60deg above horizon, then the error (the amount by which the actual figure deviates from the apparent figure) on the lower part of the circle is only about 15m whereas the error on the upper part is a massive 32m ! Hence, you have to extend the upper part of your loop more than the lower part by quite a margin to make it look round.