I am making plans to build shelves for an open pantry in my kitchen. The plans are in the attachment.

Need opinions/insights:
-- My idea is to use 3/4" MDF as the shelf material.

-- The shelves will be 'banded" all sides with 6063 aluminum channel that is 3/4" in all the dimensions and 1/8" thick except the rear.

-- The rear of the shelves will be mounted in channel that is premounted in the wall.

-- Next, the real question, do you think I can get away with using only two brackets 48" apart for support? The lower 3 shelves will have legs since they jut out 20" from the wall.

Is that clear as mud?

I thank you all in advance for your help.