I, too have an older Whalen stand. If you call them and ask that question, they will definitely tell you not to do it. It's still your call, but personally I wouldn't go that far past the design spec.
But what you probably can do, if you saved all the parts and you don't mind a couple hours of work, is reconfigure the stand and mount the TV to the wall. Even if you didn't save the extra parts, they might be able to sell you what you need.
Or, you could just buy a new stand and either sell or re-purpose that one. I have a slightly older version of this model, it's solid as a rock.