Questions about pulling a fifth-wheel with a half ton TV

I think that "80% rule" exist to provide some room for error. For example, most people don't actually weigh their trailer loaded so they may think that it's withing the tow rating when it actually isn't. Or, maybe the truck is aging and parts are worn. Do I really want to tow 100% of the rating? Not sure. If I want to keep it forever, maybe it will last a little longer with a liter load. The 80% isn't written in stone.Just to suggest liter better than heavier.