One feature of the .post and .page files is that Emacs (or another editor) does not know what mode to use. This can be solved in Emacs with magic-mode-alist, which is how I am doing it in coleslaw mode. A simpler way is to put a line like
-*-mode-goes-here-*-
on the first line of the file. Such a thing would obsolete half the code in coleslaw mode.