When I drove the bigger panel vans, the winds or passing vehicles made you grab the wheel with both hands and hold on. Pulling the 29' TT with P-rated tires is much better. But the LT tires will stop the left and right rocking, when you get hit by wind from the weather or a truck. Yes, heavier weight will help but the LT tires will help a lot.
Anyone driving over 65 mph pulling a TT is nuts. WHY!!!! Because the trailer tires are only rated to 65 mph and know for a fact that going 70 to 75 mph will blow them. I've seen many family, friends, and coworkers blow their tires going at such speeds and have no idea why it keeps happening. Now they know and came to their senses and slowed down.
Many places, the speed limit is 65 mph if pulling a trailer.