I run 45 psi on my 13’ Scamp, which is similarly configured on the lighter side. That’s 5 psi less than the sidewall maximum of 50 psi recommended by Scamp. We only do short off-highway forays, and I don’t do anything to tire pressure. For longer travel on improved back roads, I’m thinking you might go down an additional 5-10 psi. That’s still well within load-inflation minimums for the stock ST
tires. That assumes lower speeds, and you need to remember to air back up for high speed highway towing.
ST tires aren’t really meant for serious off-highway use.