Continuing with the egg capsule, I cut a circular bulkhead out of corrugated cardboard and glued it in. Off center — the asymmetry of the two egg pieces means the midpoint between the eggs will not be at the center of the extension tube. So I measured and put the bulkhead about at the egg-egg midpoint. I painted the bulkhead with epoxy, to reduce absorption of, erm, crash-related substances. Then I added pieces of foam cut from a plastic egg carton, even though I doubt whoever specced that foam for egg containment didn’t have quite this application in mind.
It’ll be longer and fatter; more weight and more drag, but more room for padding. I may end up using both. Not simultaneously, mind you.
I’m so far building it pretty much the same way. It’s too big around to make an extension tube out of BT-70, but I found a cookie tube that was slightly too wide and cut it to size: