I seem to remember that the measurement method is different among a few companies. However, COG isn't static. It will move based on where you put your supplies/water/gear, etc. Also, the affect on your handling will vary depending on how many people are in the vehicle and/or what supplies you carry.
Practically speaking, larger campers are built for DRWs. If you have one that is in good working order, you are probably good to go. Sure, your truck may be worse than someone else's or a little better.
However, if you want a more capable truck, there's not a lot wrong with overkill.