"Anyway we are looking at 21-26' Winne TTs with GVWR of 7000/7500 lbs. Would be towing with a 2014 5.8ltr 4dr 2wd Tundra SR with tow pkg and aftermarket break controller. It's rated to tow up to 11,200 lbs. BUT eventually someone correctly pointed out that the hitch is only rated up to 5,000 lbs and that I would need a WD system"
My Winnie is rated GVWR 7,000 pounds but fully loaded and wet it's just barely over 5,000, and its pulls great with my Tahoe's 1,595 payload capacity. Very close to what you have. I would suggest upgrading your hitch.