I've actually finished the control panel... 3 years later, lol.
I used an IDE to USB and a IDE to slim-line drive adapter for the DVD drive.
The USB ports are just a stripped 2 port USB hub.
In order to get the joystick port flush I actually have the male end facing out and use a gender changer for the joystick.
The audio ports are for head phones, mic, and line in, which I just used 3 1/8th mini-jack extension cables.
The knob controls the audio volume. I took apart a creative 5.1 audio control knob and put it back together around the wood.

Also I noticed the first post seemed to have lost all the images of my cab they can be found at;
http://fathertom.net/mame/pictures/-FTen