Unless they've changed something on the Omniums to allow it to work with a 73mm bb shell, you can't put spacers under either side of the GXP cups. The limiting factor here is the crank spindle. It's designed for a 68mm bb shell and by spacing either cup out, there won't be enough splines exposed for full purchase of the NDS crank.
If you're having clearance issues on your chainstay, you are probably SOL. That crankset is a track crank designed to work with heavily manipulated, narrow chainstays. The spider and/or crank may not clear many fixed gear road frames.
In other words, gospastic, although grouchy, is correct.