Learning from what works. What do humans do to jump out of things with paragliders and high aspect ratio wings.. its not like a parachute. One must avoid cravats and the lines are thinner. Not meant for shock inflation. 

I based my design directly off of the JUSTAcro D-Bag designed by Pal Takats. I also used his packing method.  

First drawing.

Made it out of paper next.

Outside of bag. Note attachment points Velcro direction. Flaps. And reinforcements on the line keeper flap

View of inside portion of bag. 

Packed