I'm not sure this would be desirable, I'm having a -lot- of difficulty not leaning the n900 forwards or backwards when i don't mean to... I can only imagine how frustrating it would be to keep drifting upwards and downwards, especially since you never really need to look up or down except when you're firing, and it autoaims anyways.

I'd love to know if you can disable the forward/backward tilt of the accelerometer but keep the left/right turning of it. It's a little fickle but fun to turn using it, but suuuuper frustrating to use it for forward/backwards movement (and inconsistent, if anything it should do as tangs suggested... mixing movement and turning into the same control is really awkward).

The best setup I've found by playing with it for about 15 minutes is:

fire - ctrl (proximity sensor is an awesome idea but a little difficult to use... would be really great if being closer meant "fire faster", but that doesn't really apply to this game so it seems overkill)
movement - arrow keys (set left/right as strafe left/right instead of turning in the controls menu and leave up/down as move forwards/backwards)
turning - accelerometer (just try not to lean forward or backwards too much or it will override your pressing of the up or down arrow)

The only problem is the forward/backwards movement with the accelerometer if you accidently lean forward, but aside from that it's surprisingly comfortable for such a little guy