160 lb. trailer, 4:80X12, 4ply rated tires, side walls advise 60 lbs. max PSI. Spring suspension(two leafs, third middle leaf removed) with approx. 50-100 lbs, cargo. What tire press would be a good balance? I started at 60 psi and am now down to 40psi.with no noticeable difference in ride. Many years with a Bushtec at 35psi. all the time.