jeff I am going to do a post in the near future that will expand on this but will put a little of it here for informational purposes. My wife and I have a 13 foot Uhaul
with the weight
fully loaded at 1640 lbs ( weighed at Bandon this summer ). We have pulled it with a Ford F-150 4.6 litre V8 engine 3.73 rear end mileage 11 to 13 mpg, a friends Silverado 4.3 litre V6 with a 3.23 rear end mileage 11 to 12, my ( now sold ) Honda Ridgeline 3.5 litre V6 rear end ratio unknown with mileage at 8 to 11 mpg, my wife's Honda CRV 2.5 litre 4 cylinder rear end ratio unknown with mileage at 17 to 19 and finally with a Dodge Ram 4.7 litre V8 engine 3.55 or maybe 3.73 rear end with mileage at 14. Interestingly enough the best mileage was the "underpowered compared to all the others" Honda CRV. Strangely the CRV seemed to be operating at less of a strain than the Silverado, and Ridgeline and I could maintain speed as easily as any of the other tow vehicles. The trip with the CRV was over the same type of terrain as all the other vehicles and totaled 3800 miles through the mountain west at high elevations and over several mountain ranges. So much for underpowered in my experience. Now to your problem. As noted by others your total weight
is substantial. Is it a possibility that the weight
is "squatting" the Scamp
enough to create and "air dam" under the trailer ? This would fit with your description, paraphrased, of "tows o.k. on the flat but slows down noticeably on the hills".