Pioneer IPod Cable CD-IU200VM for F500BT

[StupidPig]

I'm thinking on make the IPod cable dockable with the F500 cradle, by making something like this:

 

F500BT AV/USB jacks -------> Metal contact pads at the back of battery cover -> Metal contact pads at the front left side of the cradle ---> IPod Touch

 

Basically the idea is cutting the CD-IU200VM cable in the middle, then connect them again with some metal pads like the one used for connecting the cradle and the F500.

 

I don't really want to cut the original cable since it is kind of expansive (almost $50), just to try whether the concept works or not, so I brought a cheap (about $10) IPod USB/AV cable from ebay, but when I try to connect that cable with F500 (before cutting), the Ipod said "This accessory is not supported". What special with the Pioneer IPod cable? I tried different ways to connect, like using the USB cable come with the IPod, the F500 can control it but obvious no sound as no AV plugs on that cable. I also tried to use that cheap USB/AV cable by just connecting the AV part, and I can listen and watch video on F500 in AV mode, but can't control it via the F500 as the USB is not connected.