I'd like to blame my schedule delay on storm cleanup/repairs, continued 100+ degree heat and a power outage due to an over heated substation. But I can't.
First off, I realized that, if I add a ~3.5" stuffer tube between the motor mount and the end of the body, then the allowable engine offset is less than on a 4" tube. This temporarily threw me for a loop. I though about options and finally just reduced the offset. I'll have to adjust the tabs on the lower fins accordingly.
The stuffer was attached and I proceeded to the tail cone. I have some thin blue foam insulation left over from a siding job. This proved to be close to the right thickness so I cut a strip and glued it to the end of the stuffer. It was flexible enough to wrap nicely. So far, so good. But, here's where the heat must have gotten to me. I thought I could trim it using a small craft hot wire cutter. Let's just say I should have stopped and tried something else. It was a mess and required a LOT of Fill'n'Finish. I cut a slice of poster board to provide a better surface than the combination of filler and raw blue foam. It still needs work and will never be perfect.
I have yet to decide on where to attach the shock tether, split the rocket, etc. My latest concern is the amount of volume in 40" of 3.9" tube and add a stuffer tube to the list of things to ponder.