The straddle set up was a bit of a ***** to get setup.
Basically I just wanted to get around the seat tube and have a short straddle.
It took a bit of fiddling, but turned out pretty well. It offers as much of a mechanical advantage as drilling through the seat tube, only looking more industrial.
I made the 2 triangle plates, and used 6 pinchbolts (with nyloc nuts), and one straddle cable hanger, and 2 spokes.

http://static.flickr.com/30/47857638_9cca49842d.jpg

Thsi is the grind plate.
http://static.flickr.com/31/53086688_161c3b0f1c.jpg
It has flipped over on me, at the worst possible time.
I lost my footing on a rollout, and dragged the foot, and when I climbed back onto the pedal it was already the right way around.
Basically its weighted to always face down, but that doesn't apply when the bike is weightless.