Originally Posted by BEC

All three examples of the 1207 Phantom I have in my possession use parts which are dimensionally identical to the Alpha III fin can and nose cone.

A goodly chunk - I don't know right now the specifics - of the 1207 Phantom's run had a 4 inch piece of PST-50 for the body tube. This again includes all three examples I have. However the catalog height dimension was never changed when the kits did. You're suggesting that perhaps the initial 1207s had a 6-inch-long piece of PST-50 which would make that model the same size as the current Alpha VI and the nameless Alpha III sibling in the 5302 Rocket Science Starter Set.

For the two 1207s I've built, as I've mentioned before, I substituted a 5.5-inch-long section of PST-50 so that they're the same size as an Alpha III/IV.