My design will be extremely similar to this: http://zedomax.com/blog/wp-content/u...07/02/cnc2.jpg

So I don't have the gantry sides to be too concerned with, the 3 foot section will be mounted directly to the 4 foot rails and the 4 foot rails raised off the bed to allow for height. Just my machine will be made from aluminium extrusions since it's a simpler construction process.

Hopefully that helps!