There is a known problem specifically with the LW Pro 810 PPD that causes it to always default to "US Letter Small". This has been reported to engineering and they have resolved it in the LW Pro 810 PPD that will be shipping with the next revision of LaserWriter 8, beyond 8.4.3.
Note: The Option-Save trick with Page Setup works for the most part, however, there are some applications that do not take advantage of it.