As Mike said, if you start a pack through the home cooked list "ending" takes you to the menu. It only triggers the ending film if you start it with Save & Run from JCS, or if you start it from the singleplayer episodes menu.

As for my method sucking... well, if someone doesn't have the self restraint not to watch all the cutscenes until they are meant to be watched then that's their problem. Unless Jazz is hacked to allow the loading of avis, or flcs between levels, this is the only way to show multiple non-level cutscenes in a level pack.