This is for the truly twisted!
And for simplicity, I'm basing the following on the old-timey, standard military parachute I jumped with in the Air Force. Cd 1.35.
If you know your Cd and Af, then you know your CdA.
To get the diameter of a parachute of equivalent drag as your vehicle, use:
[ ( square-root of ( CdA / 1.35 ) / pi ) X 2 ] = diameter
