21” x 93” each shelf will have 2 more horizontal supports under 3/4” osb. The currently unsupported corner in the pic along the wall will have 2x4’s inserted in between the horizontal wall boards for support. I know adding a vertical 2x4 on the middle of the front will give it more strength, but will I be sacrificing ease of accessibility in the name of over building? What say you Ingo, add the 2x4 or finish out as planned??