Semi floating shelf bracket

I call these semi floating shelf brackets because you can still see the bracket underneath slightly. I have a .8 in X 24in solid Red Oak board I used for the shelf, utilizing 2 brackets on each end. The shelf does hold well but has a slight droop, It could us a 3rd middle support, which gives you a rough estimate about how much weight they will hold currently. Brackets where printed with 20% infill and I'm using PLA+ from GST3D. The brackets are roughly 150mm X 75mm X 20mm. I mounted the brackets to the wall and leveled them before mounting the board to the bracket.