Chucking?

Since you don't own a 5th wheel then don't worry about it until you get one. Not all 5th wheels have a chucking problem. And some are worse than others. It also depends on the truck too. I've read comments from others that own the same 5th wheel as I do and they report a smooth no chucking towing experience, but they have a different truck than I do.
You can always change the king pin if needed after you buy one.