When you are choosing an airfoil you are actually choosing different sorts of efficiency. If you choose building efficiency you will go after an airfoil that suits your DIY building board. The building board is often flat and so is the underside of an airfoil like the Aquila. If you are choosing one of the other airfoils, you are probably aiming at aerodynamic efficiency of some sort, which will give you longer flights and everlasting joy. If your connection at the DIY-shop is so good that you can buy “SD 7037”- or “MH 32”-building boards I’ll be your friend! Well you can actually make building boards of foam covered with balsa or abaci. Aerodynamic efficiency is never the same and when talking about aerodynamic efficiency there is always a lot of compromises involved. Efficiency can be the all-and-out racing machine for dynamic soaring or speed records; it can be the dead air F3J machine build with free flight technology that flies for 10 minutes before 6 am from at single-man-tow-without-pulley launch, or it can be anywhere in-between. Some of the compromises can of course be of the non-aerodynamic type. Some of the compromises do even have room for a little man in a cockpit or a small wheel on the belly together with some aerodynamic efficiency. But compromises that involve aerodynamic efficiency can never incorporate an airfoil like the Aquila!