I really liked the original concept but wanted shorter brackets that fit 6 gauge screws well so I modeled one from scratch.

Also made a 3-panel corner bracket (otherwise you'd need 3 of the 2-panel brackets to achieve the same thing).

Print in the orientation it loads (rotate the overhangs towards your parts cooling fan if necessary), no supports.

Update: small rounds at weak points added. Bambu Slicer likes to put seams at the weak point, even with a radius (Super Slicer does not), consider manually painting seams in your slicer if your slicer is putting seams on the stress concentration. The yellow brackets in my pictures are of the earlier version - you can see that the seams are at the worst place.