I tried to make these out of 2x2x1/4 steel angle as I was having a hard time locating 2x2x3/16" aluminum angle where i live (Grand Junction, CO) as my options are limited. I used my drill press to drill the holes and I was not happy with the accuracy of the holes. I learned a few lessons: a) buy new drill bits (good grade, not cheap ones) b) steel is much harder to drill & cut than aluminum! After reaching out to another local EAB builder he has some 2x2x1/4" aluminum angle laying around so he brought it over and I remade the brackets. These new ones worked out great. I also found that using my cheap-o plastic miter box jig to cut the aluminum with a hacksaw made the cut more accurate too! I don't have a band saw so I'm cutting everything with the hacksaw. My workbench surface is very level (I was surprised) but I still wanted to ensure the spars are level end-to-end. I built a water level, which was really fun, to ensure everything is level...and stays that way. I also pulled a string line from end to end and ensured no bowing when leveling the AFT spar.