After several false starts, I finally got my vehicle to remain stable and balanced.
As you can see from the pics, there's no motor so it only coasts down hill at the moment, but I only intended this to be a proof of concept type deal - eventually (probably next summer) I'm going to start with a running motorcycle or scooter and modify the front end to make it a tilting three wheeler. Before I spent any real money on a running vehicle, I needed to know I could make the electronic control portion work, which I've now done. Lots of learning points so far that made the effort worth while. The follow on design will be dual redundant from top to bottom, have a much faster and more powerful steering servo, and a tilt lock mechanism for slow speed where counter-steer is no longer effective.

http://picasaweb.google.com/soderberg.eric/DBW3WheelTiltControl?authkey=Gv1sRgCIzBzoK-8MWDeA&feat=directlink

Also, here's the link to my simulation for the vehicle response. It was very helpful to have in debugging the code and understanding what was happening.

https://docs.google.com/leaf?id=0B8Rk0npCAdiOOGU3YjdmOGYtYjBhZi00MjVjLTg1ZGYtMzYzODk3M2RlN2Zh&hl=en&authkey=CIe5xPMG

Damm what a lot of work, I almost understand what you are doing. That spreadsheet looks intense it's cool generating it from the simulation.

Ralph