Don't give up on the three inch channel too quickly. If I remember
correctly the stress varies as the cube of the span. So think about
having some supports that go from the ramp to the ground. The height
adjustment so they are really supporting part of the load could be
adjusting the height of the support or varying where the support
attaches to the ramp. If you have two supports per ramp, then the span
is less than 4 feet, and you gain a bit in that the support is not a
simple support too.


Dan