Weght limit for SolidSteel shelf/cones?

Your are right, aluminum cones will not support the load you mention. Best to find steel or brass just to be safe, otherwise you new table will be shortly on the floor, in many pieces.

If you are thinking that the cones will give way..not a chance at all. their small foot print should have enough pounds per square inch to support three times that weight and more. I would be more worried about the shelf either warping or a possible crack. You could substitute the shelf if thin walled with a thick butcher block top with cones.

The aluminum cones will support the load. They are an aluminum alloy and are stronger/harder than the aluminum you typically think of. I have a 5.5 rack with a 2" thick maple top shelf with a VPI Aries 2 Extended. I don't know how much it weighs, but it is certainly more than 50 pounds. It has been there for four years without a problem. Don't worry about it.

I've used a Solid Steel rack with individual components weighing close to 100lbs. It's not a problem.