qedude wrote:

I should have been clearer the flex is defintely coming from the 8x8 tubing and
not the base or the concrete. The tube does not appear to be twisting and flex
is does not seem to occur diagonally. I need about a 50% improvement to get
where I want it.

If you have Al welding facilities, weld four pieces of (say) 1/4" plate
3 or 4" wide and the length of the column to the four corners of the
column sticking out like cooling fins. This will stiffen it up
significantly in bending but won't do anything significant for torsion.

Ted