Originally Posted by CPMcGraw

Is the balsa bulkhead stuck in the clear tube bored out?

The design would only need ONE thrust ring, if the upper engine casing extended rearward about 3/8". IIRC, the two casings would be taped together first, then friction-fit into the sustainer, and then the booster would simply be friction-fit over the booster casing. There is no room for any sort of extra ring within the booster body.

My curiosity is about that "other tube", and whether it is an empty casing used as a push tool, or if it is another thin-wall booster tube. If this is just another booster tube, then what we have is an optional payload capsule, using the second bulkhead. The NC slipped into the top of it.

ADDENDUM: Remember the wording of the catalog -- "Can be flown without payload capsule"... This might have been what Estes intended, using the plain-paper tube when you didn't want to use the clear plastic capsule. You can't fly the rocket without that extra length, it would have been unstable.