Based on my Tundra, rated to tow 10K and I'm towing 6,500 lbs. or so, I'd suggest that you stay at least under 8K, and 7,500 is probably a better goal to shoot for. No doubt, with a good WD hitch, you can do more and get by even if exceeding the payload weight by a little, but it will take a toll on the truck and may not be the best for driving and handling. Keep in mind when they say a trailer has a dry weight of 7,500 lbs., that doesn't include the weight of options, propane, any water, etc.
Another way to look at it is to use the GVWR and check how much they are allowing for cargo. My trailer had a dry weight of just under 5K. But with added slide out awning, propane tanks filled, and loaded with all gear except for some food & drink, and some clothing, the trailer weighed 6,200 lbs. at the scales. So, with some other mods and with all gear, I figure I'm pulling 6,500 lbs. and really wouldn't want to pull much more. The GVWR for my trailer is 7,500 lbs. It's only two of us, but truck bed gets loaded with 2 folding bikes, blue tote, tool bucket, 5lb. propane tank for grill, a little firewood and other misc. stuff.
