Here is a link to a discussion topic that Ron Dittmer began at the end of 2018. He mentions some tires that carry better load ratings than the standard 2680 pounds found on the normal "E" series tire (though I believe that all are still LT-type tires):
https://forum.phoenixusarv.com/index.php?topic=3497.msg29723#msg29723You might also do a quick forum search on "Rickson". That should bring up some discussions of the Rickson wheels, which several PC'ers adopted to greatly improve load carrying capability over the standard units. The Ricksons are 17.5 inch wheels rather than 16, but use a different tire configuration (215/75R17.5) which results in approximately the same final tire diameter. Since these are load range "F" and "G" tires, they can bump each tire's load rating by almost 1000 pounds. Downside is that this is an expensive move, since the new wheels will add about $900 to your new tire bill, the tires are more expensive as well, and then new wheel covers would add another $400 to that.
The Ricksons have primarily been a solution for the 31-foot PC's with multiple slides that are virtually operating at load capacity on some of the tires as they roll new out of Elkhart. With your 2551, they would probably be overkill, but would put you in a regular "truck" tire, as opposed to "LT". The units like Ron identifies in his post, would be a much less expensive way to upgrade ratings to some extent when you change out your tires.
All the best, Mike