for my Truck / travel trailer.. I use the Garmin Dezl 770 " Trucker ".. unit with POI factory RV download files for RV items..
way better.. designed for semi-truck users.. works well 2 years and 12,000 miles..
if you have a motorhome.. use the box truck settings... for truck and trailer use the semi-truck/trailer.. and add your size into it.
with the POI files.. its is an RV gps with truck features ..
with ANY GPS.. never follow it blindly... know where you are going. and allow the GPS keep you on your route...
also the 770 allowed a finger to change route on the fly...
hill and sharp turn warnings... speed change alarms..