jmtandem, from your calculation, the Jayco is probably within the range, but considering the passengers, my max tongue weight is probably around 400. Like I said, I will weigh the vehicle sometime this week and find out. I am really thinking about R-Pod or T@B just because I don't want to go too close to the limit...
It is good that you are thinking about all this
before you purchase not after. That speaks volumes to your ability to be safe. Congratulations on whatever you purchase. I think you will find that with RV's it is never the first one that is the final one and you will want bigger and that will mean a bigger more stout tow vehicle. As others have indicated always use trailer's gross weight not dry weights or brochure weights for your calcualtions. Above 40-45 mph the trailer's wind resistance can be a major issue especially if the wind is blowing and, of course, in the mountains the tow vehicle will work much harder climbing and you will need to be sure it can also safely get you down as well. Good luck.