The previous owner pf our Wong was significantly larger than I am, and he upgraded the suspension on the bike. My experience with the suspension may differ from yours.
We used to ride with the preload set at 10, but we were dragging pegs too often.
We have our pre-load adjusted to at least 20 to help minimize the grinding. Then the grinding is usually just the pegs. We will occasionally grind the mounting hardware for the highway pegs in the mountains, but what are you going to do?
Try riding with the preload all the way to the max and see if that improves things. Your welcome to try my Wing to see if the feels the same.