Simply having a hard disk uses memory, as a certain amount is reserved for buffers etc. You can actually change this in your startup sequence by using the addbuffers command with a negative buffer count.
2MB of chip ram is not going to get you far, no matter how much you strip from your configuration.
The best thing you can do is add more memory. Even a basic 4MB of trapdoor ram will be a significant improvement in performance terms.
-edit-
How are you supporting the 6GB drive btw? I thought that you needed OS3.5/3.9 or 3.1 with NSD to support drives > 4GB