The nylon wedge collar under the nut seemed almost fused to the aluminum tube. Even with the nut completely off the collar initially would not budge to allow me to adjust the height.
It took a while but I held the aluminum tube with a pair of rubber padded spark plug boot pliers so as to not damage the tube, and slide a 1/2" open end wrench under the collar, some silicon spray, and kept working it until the collar freed up.
I had to move it down 7/16" to get it 1/16" from the bottom.
The low fuel light and shutoff was occurring at more than 1/4 tank on the gauge. Now it occurs at just under 1/8 tank on the gauge.