What if you made it so that instead of needing to track to slow your descent, you could just fall normal and still be slowed down? I'm thinking that if you connected a sheet between your wrists and ankles (like a flying squirrel), you could slow down quite a bit. Then if you left the wings, and maybe built a tail or had large "fins" you'd have greater control and a slower fall. obviously at some point, if it were large enough it'd work, but the question is, would it be too cumbersome or difficult to control? I don't have much experience or knowledge at all about this, so please lay into the idea if its bad :)