I learned to jump...and do still occasionally jump...round canopies (MC-1B/C, GQ Aeroconical). Never jumped a square other than a few tandems. Anyway, with the bravos and charlies I was told pull down the rear risers as far as I could about 15-20 feet off the ground to help soften the landing. It works (I once made a stand-up quite unintentionally) but I don't know why. Can someone explain the physics/aerodynamics of this?