Pathfinder - X17C experience
I have a setup that is close to yours. A 2006 Pathfinder and an X17C. Indiana is mostly flat but I found the Pathfinder to have plenty of towing power. I did tow in 3 and found that to run 55 I was at about 3400 RPM at to go 60 would push it to about 3700 RPM. On a couple of occasions I moved it to D with the overdrive off. The truck did not seem to struggle and the RPMs dropped about 700 - 1000 RPM. I wasn't comfortable leaving it there without a transmission temperature gauge but the "hunting" for a gear that I've read about did not seem to be a problem in 3 or D (with overdrive off). I think you should be be fine if you make sure the OD is off. Gas mileage is another story but that, I've learned, is a universal, unavoidable law of towing.