We agree with prior posts - we tow a Lance 1685 (20'9") with a 2006 4 Runner 6 cyl. Towing capacity is 5000#, trailer is 3800# dry, but way too close to our max loaded.
After 10,000 miles, here's a post I wrote on Pros and Cons:
http://trailertraveler.net/towing-travel-trailer-with-a-6-cylinder-4-runner/ My husband said I could buy a trailer, but couldn't have a new truck... so the compromise. One of these days we'll get a new tow vehicle and we'll have more margin for safety. In the meantime, a 24' trailer is going to weigh alot more than our 20 footer, we wouldn't do it. Just our .02 cents worth...