I needed some straight brackets so I used one of the bracket's from Phaeteon's 2020 T and L bracket variations. I made a 5 hole and 4 hole version (and now a 3). I also made a four hole with a built in corner bracket (and now a 3). The corner bracket came from David Creel's Corner Bracket. Version 2 has the straight and corner bracket being about the same size. The first version is more like the one I am going to use from my project which has the 4 hole part being smaller.

When I made the 5 hole it warped and I realized it was too big. For my project a 3 hole with corner and a four hole is what I need.