The egg separates in the middle, so I've got a nose cone and tail cone. Just measure the diameter at the "equator" and the height, enter them as an elliptical nose cone in Rocksim. The bottom section is more pointed, but still elliptical. A tail cone section from the "equator" down to the bottom, with a fictitious diameter of 0.01, and you've got the general egg shape and dimensions.
Adding the interior 98mm airframe for parachute and motor section meant approximating where the cut would be, and shortening the tail cone, keeping the original shape as much as possible. Good enough for a sim.
Tried parabolic instead of elliptical, but they come out too pointy. Elliptical works for me, but you'll have to ask the chicken which formula she uses.