The mats can handle cattle and horses, so the weight isn't a problem, if that's what you're asking. I'd be more concerned about the rack not being bolted down. If your ceiling is high, then the thickness of two or three layers of 3/4” plywood isn't a factor, and you can solidly bolt the rack to that through the stall mat.
You say you're not building a platform YET. What is the nature of the delay?