Capt Pit Bull
If you want to talk about 'drag' then in that language one would have to say say that a parachute Cd 'effectively' varies with altitude due to porosity effects. But that is a bad way to think of things because drag is an aero concept and porosity is not - hence the use of the term porosity
The opening shock loads are merely the peak loads measured during the opening process and depend on how the canopy is designed, whether it uses taschengerts to control the incidence of the peripheral hem during opening and so on. Complex issues.
JF