We've pulled our 2005 Honda Element from pillar to post behind our 32' Winnebago Adventurer with a gasoline Chevy 454 without any problems. Your speed up and down long grades is more a matter of your attitude and patience than your coach's horsepower or torque.
Let the cruise control take care of things on the uphill stretches and don't fret the high engine rpm's (as the engine is designed for that). Downshift to the lowest gear on the steep downward slopes and appreciate that you are driving safely. Take it slow. This is not a race.
And don't ride the brakes downhill. Let the engine do the braking and apply brakes intermittently only as needed. My DW says, "Don't worry about the people behind you. You're doing them a favor by slowing them down!"
Good luck in your travels!