Looking at the Slingshot range of foils and wondering what the difference is with the rear foil on some having the winglets on the end of the foil facing up on some and down on others . Big difference and why ?

Any aeronautical types out there ?

The way it was explained to me (not an engineer) is that the 42 stab is designed to be mounted on the top of the fuse, tips up. The 48 is designed to be mounted on the bottom of the fuse, tips down. They both use the same rear shim so this means that the stabs are designed completely differently for angles of attack. You cannot mount the 48 on the top for example--lift will be totally wrong.