I am pulling a 295 RK Mountaineer with a 2012 F250 4X4 GAS 3.73, and have about 1200 miles to go on a 6000+ mile 5-week trip from Indiana thru Denver, Reno, Tahoe, Moab, San Francisco, Yosemite, the Fed parks in N AZ and S Utah. Right now, in Santa Fe NM.
Lots and lots of mountains on the trip. All is going very well. Averaging 9.3 mpg for the entire trip, despite the extreme hills. This same equipment has pulled the trailer to the East coast twice, and Destin FL twice. My truck is closing in on 20K miles, most of which are tow miles.
I assume my 29.5 weighs a little more than a 28.5, but you didn't state a weight for the trailer. My trailer is about 11.5K lbs. Anyway, it works great for me, and no regrets on the trailer or the GAS pickup.