The toyos I posted are the highest rated tires I know of without going to commercial (19.5's) which is basically pressure limited. The air holds the weight, not so much the tire..but tire construction allows the higher psi.
If your over your current tires by a significant amount, you might not have a choice without going to a drw or 19.5's. It's only something you determine in the end, some go over on the manufacture limits and do so without issue, some get a F550 for their pop up camper.
I'd see what your new TC weighs in at.
Curious...I'm getting a 992 in the spring, what is your empty and wet weight and do you have a genset and ac?
Oh and what is the load capabilities of the 245's your looking at? Your vision wheels are limited to 4500 lbs. so if your tires are more...the wheels are the limit. Mine were, I had tires rated to 6295 lbs. Way over the wheels.