I checked and noticed the R187's had a load rating of "F" which should be more than adequate for over the highway travels.
On our first coach we had Michelin 8Rx19.5' with a load rating of "D" and they worked just fine. As an alternative, if you have adequate spacing between your duals, you might consider going with 225/70R19.5's.
The diameter of the 225's is 32.2" compared to 33.6" on the 8R's; tread width of the 225's is 8.5" compared to 8.0" on the 8R's, and revolution per mile is 645 on the 225's and 618 on the 8R's.
Good luck with your choice
Jim & SherrySeward
2000 Residency 3790 v10 w/tags 5 Star tune & Banks system Suzuki XL7 toad