Wow you got two adapters eh?
I bet that cost a pretty penny with both the 5-1 and Xbox 360 converters. But $59 is a pretty good deal.
You might have one tiny problem. I cannot start up the Xbox 360 while the X arcade is plugged in. My xbox 360 refuses to boot (it says in the documentation it
should boot), so I have to do the old cable switcheroo.
I don't think it is a major problem if you are a casual user, but if you are going to have them in an arcade cabinet, it might be.
I know this was not always the case so there might have been an update somewhere that prevented 3rd party adapters from authenticating.
I know I have this same problem with the PS3 and the 5-1 with some games.
I also just recently bought the Cronus adapter which boots with a Xbox 360 controller with no issues. So I think the proof is in the pudding i.e 3rd acceptable party controllers.
OK look at this:
This is the layout of the two Xbox 360 adapters via the 5-1. You should be able to determine which button does what.
As a bonus you could also install a PC into your arcade cab as the USB is compatible.
So how are you going to boot your xbox 360 without unplugging and plugging the USB?
Simples.
I have one of these:

Mine looks exactly like this but mine have 4 outputs on each side of the box and it looks like an octopus.

You will have to buy A>B cables but I get mine on Ebay for cheap.
I use it to switch all my USB devices between 4 game units. If the USB is not selected (this is an electronic switcher) the device is not recognised on the device. So you can have both PC, Xbox 360 connected in your cab and just select what device you want it to work with. Yes it is a pain in the bum, but you have just bought a device that has a dual purpose. Well at least you can play Mame and console emulators on the PC in your cab. But that is not all. Since you are using the 5-1 and the Xbox 360 adapter the dreaded 6 key limitation is gone on the PC.
Associated whiners and lamers (you know who you are) rejoice.

One day I too will follow your lead and put all my Xarcade stuff into a dedicated arcade cabinet. I think you are on the right track, and if you follow my advice (don't buy the manual switchbox!!!) you will have a pretty cool cab. Just make sure you make a proper control panel with your X arcade innards.

Let us know how you get on.
