Paul,  This is not aircraft related.   I am working with square  aluminum tubing 6061 T6 x 1.5" x .125 wall and I would like to lighten  it as we have done on the S-beam using 1" holes spaced on 1.25"  centers.   I need an expert opinion on how this effects the strength  of the of the tube.  The tube needs to resist deformation vertically  but horizontally it does not see much pressure.  The holes would be in  the horizontal.   Thanks,  Jerry

It will affect the strength very little. The load is best applied one side
or the other of the holes. How much You will have the wait until I get back
from Fl in a couple of days.

Paul Lamar