Unless you lay planks across the tops of the bed rails, stand 55 gallon drums on top of that, and set the camper on top of the barrels, "top heavy" is not even a mild concern.
Like others have said, if you are considering selling it, it's not your problem. Of course people show up with no clue, but it's easier and more responsible to turn them away than try to shoehorn things just to get your money. The guy I bought my TC from turned away several that showed up with F150 shortbeds. While my Palomino B1500 is light enough for an F150 if you use a little creative bookkeeping it would snap in half on a short bed truck. Come to find out years later my TC is slightly banana-shaped as it is.