Mike,
You're right, up to a point. Having 16 bit grayscale, rather than 8 bit, means the file is going to be almost twice as big. On another current thread, one poster was mentioning having problems while transferring large files. It seems that all pattern files go into one large file so then RAM capacity of your machine becomes ultra-important. Also, it tells me, because of the other thread, to back up this file almost daily, the simplest doing sequential back-ups.
Chief