ALL ST tires are rated to 65 mph. Most of those you read whinning about cheap Chinese tires have been towing faster than that (or overloaded or both).
SLOW DOWN RVing is about relaxation. Going slower means less chance of a blow out, better fuel mileage, fewer trips to the ER or morgue. Remember you are towing a house and it takes a lot longer to stop.
2004 Chev Silverado Duramax optioned past the max. 2009 Jayco Eagle 308 RLS 765 watts of solar, 6-6 volt batteries (696 amp hour), 2000 watt (4000 surge) whole house inverter.
188days boondocking in 2018 206/17,215/2016, 211/2015, 196/14, 247/13, 193/12