I have a 2010 Frontier Pro-4x. I also have a KZ Spree 240BHS LX and a Nissan Armada I tow that with. I would NOT pull a Travel Trailer weighing over 3500lbs ready to camp, gear and all with the Fronty. All that's been mentioned here from tongue weight to wheelbase are reasons why. One reason I did not see mentioned here was brakes.
I also have a 21 foot boat on a dual axle trailer. Boat and trailer together weigh in about 3500lbs. Fronty pulls it ok but on hills it gets less than ideal, going up and at times coming down. I do NOT consider the brakes on the frontiers to be over done. They are just "ok".
Pulling a boat and an RV are not comparable, there's little to no issue with anything passing you by with a boat, not true with a boxy RV.
Ask yourself this....How concerned with the ultimate safety of my family am I when towing the RV? The guy I bought my camper from pulled it with a Tacoma, reason he sold it was he couldn't afford a bigger truck adn he needed one badly.
Good luck, be safe!
