"Steve B" wrote in message
. ..

Appreciate it. Now's the time to do the numbers. This gives me a
clear span under the lift, converts downward bending to compression,
and just stiffens and strengthens in several ways.

Steve

Have you considered wood?
http://www.awc.org/technical/spantables/tutorial.html
In Fig 3 a 2x12x16' falls within the range you are looking for.
Pressure treated syp (Southern Yellow Pine) is nearly as strong as oak
and doesn't need protection from the weather. You do have to brace it
to stop twisting but the H center bar helps. Pick two without knots on
one side and make it the bottom.

jsw