You know, you could even do a guilt-free cutting down of the shell to 18x12, if you wanted...
But why? 14x18 works just as well for all practical purposes. That's the standard "bop" bass drum size for every other manufacturer...and Ludwig might have considered it as such as well since they sold that size too. This whole thing hinges on why Ludwig happened to use the shallower one for their catalog outfit. It might have been because someone thought it sounded better. Maybe someone felt that compactness was the major selling point of that set, so smaller was better. Maybe the smaller bass drum in the outfit gave Ludwig just a bit more profit margin on the tiny number of sets they seem to have sold. Who knows? It just happened to work out that way.
Don't get me wrong, I'd love to find a genuine Jazzette someday, complete with the little bass drum...but I don't quite get why having a 14" deep bass drum is such a deal breaker for so many, or at least a disappointment ("oh it's a 14") . Nothing wrong with Gretsch/Slingerland/Rogers/Leedy 14x18s but a Ludwig that size is second class somehow. Just kind of weird, that's all.