In days of bias ply tires, over/under inflation compared to load had a dramatic effect on tire wear patterns. With today's radials overinflation, unless it is extreme seldom causes uneven wear. Underinflation= increased wear, increased heat, low tire life. And many ST tire mfg recommend running at max inflation pressure unless replacing with a much higher load index tire.
Now, I've put 35,K miles on my small trailer and 30K+ miles on my travel trailer. In both cases i ran the original maxis tires to about 20K miles before replaceent at max pressure and wear was even. i replaced them both with Goodyear endurance one LR higher and inflated to max psi. Lower rolling resistance, lower heat buildup and again the tires are wearing very evenly. I'll stick with max or near max pressure rather than messing with actual load/tire and some magical fudge factor.
And in that time I have had NO tire failures of any kind. My neighbor has pulled two different enclosed trailers 35ft a total of over 200K miles, again inflated to max psi, load range higher, no unusual wear, no tire failures.
Now on my cars/trucks I stick with the tire placard in the for inflation.