Moving from a Bumper Pull to a 5'er

I pulled a 37ft 12,500 lb 5th wheel with a Ram 6.4 4.10 gears, and it struggled in the plains of montana with the rolling hills and wind. It had to work really really hard to get up those hills usually in 2nd gear. In second it had enough power, but it spent way to much time shifting for my liking. I had it in tow haul so it rarely went into 5th. On the flats of Minnesota and North Dakota it did fine, and the hills with no wind or a tail wind it did fine, but hills with a wind was too much for the truck. Not to much for the chassis, i didnt get blow around or have a problem with sway, the drive train just struggled to much for my liking. In the mountains going up slow it was ok, its not a race there and had plenty of power. But in state hwy 200 and US 2 with a head wind or a side wind the truck worked way to hard for my liking. Shaving off 3k lbs will probably help alot. But my experience wind was the killer. Not the hills or the weight the added drag of a head wind and hills was to much. Thats why I would like to see TFL truck guys test these trucks with a 5th wheel or bumper pull on hills with wind. Unfortunately when it is time to travel for a a camping trip. Most of us cant sit and wait a day or more until the conditions improve for better towing. That was the situation I found myself in the day we left glacier. If the wind would have been from the east I would have had to sit out the day and not bother trying to travel because the truck wouldn't have been able to do it comfortably.