My control scheme is similar. Using the mouse:
ESDF for slide right/left and forward/backward.
WR for banking.
AQ for sliding down/up.
This leaves the thumb free so you can map anything you need to the space/alt/x/c/v keys.
However, no matter what, the most important point is: can you slide in every combination of 3 axes comfortably?
I don't think this has been discussed, but if you're going to play multiplayer any time soon, you NEED to master "trichording," the art of moving along 3 axes simultaneously (ie, forward, left, up). Doing so allows you to move at a speed a factor of 1.7 greater than simply moving in one direction. If you have D1 or a port (DXX-Rebirth or D2X-XL) that can watch demos, check out everything here for a visual demonstration of what I'm talking about.
Anyway, find the demos/levels here: http://whoopass.warpcore.org/descent/chordingdemos.html
At the very least watch Deimos' crazy "3xsistr1" demo.
Check out Darktalyn's article on config here for further discussion: http://www.planetdescent.com/site/articles/darktalyn/9-12-00-darktalyn-config.asp