I saw Andrew's Q&A question: https://www.robotevents.com/VRC/2018-2019/QA/90
Would it be permissible to use a 2x2x35 90 degree aluminum angle, part 276-2304, here? The screw hole pitch doesn't quite line up with the standoffs, so a hole needs to be drilled in the 276-2304, but it works well and is very sturdy.