Thanks Chris.
I originally had considered not joining the gantry at the bottom. With this concept, the logical soloution to the twisting of the gantry was the two screw method.
I do think that the idea of raising the whole machine up some and hard framing the whole gantry is a much more efficient way to go. A singlle screw should easily push the 10" to 12" on either side without wanting to rack. The trucks should be solid and have a good span (6" to 8") on the rails.
Thanks much for the input.
The parts are starting to arrive and I am going to get a final plan drawn up to share. Nothing like the caliber of plans that I have seen on here. Just something to show which end is up.
I will also start a build log when I get to framing the thing.