I still think more TW will make it better, but is probably not a practical fix, as I mean a lot more TW.
Something else to consider. Towable RVs are different from othe types of trailers in that the TW can vary a LOT during the course of a trip. Depending on your units design and/or usage this be a little or a lot in either direction, up or down.
Food gets eaten leaves the fridge/cupboards and ends up in the black tank. Fresh water moves as well. Nobody puts their dirty clothes back with the clean ones. Propane gets used and vsnishes. If the TH has a gas station for the toys, it will empty out as well. Many other things may ride home in a different location than where they started the trip. Take all of this into consideration, and suddenly 13% may not be such a safe number after all.
