Okay, I've been hanging around here for long enough. I think I'm ready to start building. Or at least, I thought I was. I'm getting ready to order my IPAC4, OptiPAC (was thinking about waiting for the USB version), 2 T-sticks, 2 Happ rotating Supers, 2 oscar spinners, trackball, and buttons. I want to run Windows 98 2nd Ed on the cab.
I've searched and read and read and read and read about trackball, spinners, and OptiPACs.
I'm going to use swappable CPs, but wanted the above on one panel. I have a layout that I think will work, but I'm confused on the hardware to order. I read somewhere that in Windows you can really only use one Com port. If that's true, how would I hook this puppy up?
Do I order a HAPPs trackball with a PS/2 or USB interface, should I get the Interial trackball with PS/2 connection? If I do that, how will that work with the spinners attached to the OptiPAC which is then connected to a Com port? Can I use standard MAME32 for this, or am I looking at Analog MAME? I think I need Analog, but I'm not sure. 
I feel so stupid. I thought I had this all worked out and then now that I'm ready to act, I forgot everything. I suppose I should have kept better notes.
Thanks to everyone that helped me the first time. Will you please help me again?? I promis to take notes this time!!
Like most things the more this gets explained, the more confusing it gets

.
I'll try to cut through things and explain what you need to know.
First USB is really only a benefit for hot swappability or for desktop computers or many multiple controls (I am planning two trackballs, two spinners, and a steering wheel controller, either all USB or some going through the new USB I-PAC). For your setup, you don't NEED USB, not that it hurts, but it doesn't gain you anything either.
You need MAME Analog + to split the mouse axes for the spinners, and I recommend doing this.
http://www.urebelscum.speedhost.com/The whole dual driver, two port, what OS, what MAME, don't have a driver installed at startup stuff only comes into effect if you want to use two ports at the same time . . . one ps/2 and one serial trackball for marble madness, two USB trackballs for CABAL, etc. For your set-up, it won't matter.
Now the options:
You want 2 spinners, 2 rotary joysticks (assuming optical), and one trackball. There are no spinner games that also used a trackball, no rotary joy games that also used a trackball, and no spinner games that also used a rotary joy. So if the spinners and joysticks split the axis of one port, then you only need one port per game and your connections are a lot simpler.
RECOMMEND (Order is not important): Hook Opti-pac port 1 to Serial Port 1 on the PC. Hook Spinner 1 to Opti-PAC Port 1 Rotary X1 and X2, Hook Spinner 2 to Opti-PAC Port 1 Rotary Y1 and Y2. Hook Rotary Joy 1 to Opti-PAC Port 1 Trackball X1 and X2. Hook Rotary Joy 2 to Opti-PAC Port 1 Trackball Y1 and Y2. The opti-pac will now auto-switch between the rotaries and the spinners. (whichever is moved last has control).
The trackball can now be connected to either PS/2, USB, or the least expensive option is to wire it in parallel with probably the rotary joys (higher resistance to turning) to Opti-PAC Port 1 Tracball X1, X2, Y1, and Y2.
Wiring to PS/2 or USB, the trackball will share cursor control with both the spinners and the rotary joysticks, so moving any of these controls in a trackball game, will affect gameplay. Wiring through the opti-pac, the spinners will be auto-switched, so only the rotary joysticks will possibly conflict with the trackball (and vice-versa, accidentally sending the trackball whizzing during rotary joystick games can have interesting results

)
Hopefully careful control placement will minimize this possibility, or you might want to look at swappable control panels.
Hope this helps. Post a reply if I need to confuse you more.