I have a Precept 35UN and will be getting the 5 star prior to out Yellowstone trip in August of 2017. I have heard good things about it. With that said, I have had absolutely no issues going up or down inclines, Western PA, in the Tow/haul mode, using the cruise control or simply tapping the brake on downhill for the engine brake to kick in. on several occasions the revs were up there climbing some step grades but never an issue coming down, I do believe that the 5 star is supposed to help the engine not rev as much going up steeper grades. All my grades were with car in tow.