I am getting used to your slide configuration with the space and the shift keys.

That one I'll definitely try. The last time I played Descent, which was at least 14 years ago, I used a joystick. Aahh, the old days of running it on a 233 mHz PC, with a very basic vid card.

This game will never feel right to me without my trusty Sidewinder 3D Pro.

I use a PS2 controller hooked up with a usb adapter to play these games. My setup is a little convoluted but it works pretty well once you get the hang of it.
Left Stick is Pitch and Turning
Right Stick is sliding up, down, left and right.
R1 is forward
L1 is back
R2 is primary weapon
L2 is secondary weapon
D-Pad left and right is roll
D-Pad up is switch primary
D-Pad down is switch secondary
Square is for flares
Circle is drop bomb
X is for energy->shield transfer
Triangle is for rear view
L3 is afterburner
R3 is headlight
Start is map
Select is switch bombs

So after about 10 years of playing Descent (1, 2, and 3) with only keyboard here's the best control config I've discovered: (Unless you have an anti-ghosting keyboard this WILL max it out...there's just no getting around it :)
Pitch Forward: Num 8
Pitch Backward: Num 5
Turn Left: Num 4
Turn Right: Num 6
Bank (Roll) Left: Q and Num 7
Bank (Roll) Right: E and Num 9
Accelerate: W
Reverse: S
Slide Left: A
Slide Right: D
Slide Up: Num Enter (Should be under the pinkie of your right hand...if it's not use whatever button is there ;)
Slide Down: Right Arrow Key
Fire Primary: Space
Fire Secondary: Left Shift (Once again under the pinkie of right hand...you might want to use control or something like that :)
Then you can assign Headlights, Afterburners, etc. to whatever you like. This is pretty much the only way I've discovered to Tri-chord using only a keyboard. And DANG I wish I had an anti-ghosting keyboard...cause I max it out literally EVERY time I play :/