First, the estimate is exactly that - an estimate - and is often higher than the actual download size. Still, I'm guessing that you've asked for every possible zoom level. Try omitting Levels 0 and 1, and I guarantee the total payload will then be well under 1GB. (I would confirm this myself, using the same coords, but my N800 is away for repairs.)

I personally find Level 2 appropriate for most urban navigation, and might even drop back to Level 3 or 4 on highway trips. You can of course fill in the higher detail for selected areas where you want it, instead of paying the storage penalty for the whole state.

Also, forgive me if you already know this, but if you plan to store a lot of data for Maemo Mapper, be sure to reformat your SD card with the smallest possible cluster size (512 bytes for 2GB and smaller cards, 1024 bytes for 4GB cards, 2048 bytes for 8GB cards.) Otherwise you can easily waste 90% or more of the available space.