A trailer over 20' is most likely too long for the short wheelbased 4R. Tail would wag the dog as said above. After my experiences towing with my 11 4R a bit, I would keep the max weight of trailer at 4000 lbs or LESS. And that's with better than OEM tires, aftermarket shocks, rear airbags. (all of those are a must-have for towing with this vehicle). Possibly want stiffer springs all around too.
I had a 2007 tundra previously and towed my 10k pound 23' toyhauler and a smaller 18' toyhauler.