I have an ipac connecting my arcade controls. I wanted to use an Xbox 360 with it, but I knew an adapter wouldn't be a long time coming. I contacted both Andy and Haruman about options, and decided the ones that were offered were too time consuming and expensive.
Here is what I did instead. I have a PS2 adapter for the ipac, so I bought an XFPS xbox 360 adapter. This allows one to use a PS2 controller with an Xbox 360. So it was a simple matter of plugging the PS2 adapter into the ipac, and then the XFPS adapter into the PS2 adapter.
Playing like this with only one player was surprisingly effective. When I go from up to down extremely rapidly, it starts to glitch up, however.
I came to own a second xpfs like adapter, that was very clearly a knock-off. I tried using both at the same time, and it sort of worked, but next time I tried to get both on at the same time I had difficulty. I figured that I was testing my luck using both at once and stopped. But the first one still works fine.
so if you have an xfps, ps2 adapter, and ipac, be aware that you can indeed play xbox 360 using arcade controls with this method