You could, but it would get overwritten the next time you applied a standard empeg upgrade image, which includes partitioning information.
If you only use tools like Mark's upgrader and the upgrade splitter and did everything manually, then you could, and have a different sized spare partition as well.
The dynamic data partition (hda3) doesn't need to be very big. There's a =lot= of technical details in the thread Bitt linked to above, and if 16MB gives you ~22k fids, then 32MB is going to be more than double that because the 16MB includes space for saving playlists.
I think most of us with 30GB+ drives end up with at least 30k fids just using the extra space with the default partitioning.
--Nathan