I wanted to reply to my own questions here since I wasn't able to get any answers. One, mounting the Happ analog trigger joysticks underneath a control panel seems like a really tough feat. If you cut a hole big enough to slide the joystick piece through the panel, you'd definitely need some form of a giant washer so you wouldn't crack the panel, which pretty much defeats the purpose of what you are trying to do; might as well just suck it up and mount the metal plate. It also uses secure torx, so you'd have to buy a special bit to take off the handle... also seems like a really tough feat since there are wires underneath the plastic piece. I ended up just mounting my plate on top of the panel; I wasn't happy about it, but it seemed like the only choice. I'm hoping that once I add graphics/poly-whatever over it, it'll re-hide the plate enough.
Two, a Mayflash gameport to USB adapter worked just fine for me on my Win 7 x64 system. I didn't have to go digging for any drivers, either. Once I plugged it in, it detected just fine. I set the mode to "stick", and once calibrated it works great. As much as I love my u360's, games like Tron, DOT, and After Burner just NEED one of these to play more faithfully. I got a good deal on eBay for mine (around 30 after shipping), so I'd highly recommend one of these things if you are on the fence about adding one to a cabinet.
Oh, and they are built like absolute tanks, too. Happ may charge an arm and a leg for a new one, but the quality of the build is never in question. They are designed to take absolute punishment and not flinch.