I was going to recommend swapping out the MDF for slate pieces until I read your comment saying you're tired of the look. My rack is similar but with slate shelves. very heavy and solid feel. They pass the knuckle test with no ringing, just a dull thud that can be painful.
Mine is nearly ten years old and I am tired of looking at it but don't want to pay for better performance.
Mine is nearly ten years old and I am tired of looking at it but don't want to pay for better performance.