I like my Good Sam GPS 7735 LM powered by Rand McNally because it has RV settings and is advertised to only route you in a truck like route. However, towing a 40' 5th-wheel with a combined length of 57' I never trust a GPS. I also use Mountain Directory West and try to over fly the route with google maps in the satellite view. An example of why...I planed a trip from Hill City ND to Cody WY. The Rand McNally GPS routed me over Hwy 14 Alt with 10% grade over OMG hill. I rerouted the GPS to take me via Hwy 16 and only had 5% to 7% grades.