Towing with a half ton

Part of the equation, which hasn't been mentioned, is trailer frontal area. If you choose a TT that's 7' wide or 7.5' wide (versus 8'), it will tow easier with a bit better mpg and less strain on the drive train. Also a lower roofline is better than a higher roofline, same reason. I think you've gotten good advice, keep it under 6500 or 7000 lb loaded and under 25' in overall length (tongue included). Keep in mind that the heavier the TT, the heavier the hitch weight; a 7000 lb TT may well have 900 lb or more on the hitch by the time you add LP, water, etc.