I tried a bunch of different ideas and finally decided on the following.
I bought a Stanley Fat Max saw horse (collapsible and has telescoping legs). ($35 at home depot).
We designed a top that would simply bolt-on using 2 carriage bolts and wing nuts. The top is 36"x24" with a corner removed to allow access for right handed shooters. As the brace piece is secured upward, it makes the sawhorse hinge much more rigid.
The table is incredibly stable and weighs a total of 29lb's. We didn't even finish the top, as its just the prototype. We could probably remove a couple pounds, but its very light considering how stable it is and how small it stores. It is actually more stable than the permanent bench we had been using.
It can be used from 32" height to 40" height. It can also be setup to slope up or down; or be setup to be level on a side hill. If anyone wants more detailed measurements, let me know what you need and I'll measure it up for you.
It breaks down and hauls easily. The top is shown with the brace piece mounted in its storage position.
Setup for shooting on an angle
Closeup of mounting
Closeup2 of mounting
Hope that helps,