I finally did more than remove the bulk of the damage on Bed Knobs and a Broomstick, damaged (very bad zipper, and a gussetted centering ring partially torn) at last month’s NASA Ames launch (see the posting). The zipper on the forward portion of the lower part of the rocket went right down into the coupler that joined the two tubes together. I had expected to have to patch at or slightly forward of that coupler. I looked more closely today, and noticed that some of the remaining body tube had, essentially, delaminated from the tubing coupler. It turned out that the forward body tube itself could be peeled away from the coupler, leaving a pretty clean, intact, standard diameter coupler sticking just the right amount out of the aft body tube.
Instead of having to craft a complicated two-part stepped coupler, it was a very simple matter of taking the new forward body tube and gluing it to the coupler!