Some tire engineers say that you should run at the cold pressure stamped in the sidewall for at least 3 reasons.
1) Trailer tires are subjected to extreme sidewall forces and running fully inflated reduces the possibility of sidewall damage in tight turns.
2) Unless you have individual wheel weights, it's not safe to assume the weight on the wheels is evenly distributed. You could easily overload some of your tires by operating at a reduced pressure.
3) An inflation margin provides a safety net, similar to what you have on auto or light truck tires where the weight rating provides a significant margin not found on most trailer tires.
Most of the Heartland trailers using Sailun tires are in the 15,000+ GVWR territory. Unless your GVWR is way, way below that, you should probably go with 110 psi, measured in the morning, out of direct sun, before traveling.