I pull a 16 ft. car hauler loaded with a small tractor and bush hog loaded on it, total weight is about 4,900 lbs it handles it excellently with trialer brakes, however the last time I pulled it I was having problems with my controller box, and it wasn't working but was still able to stop safely. Oh, by the way I am pulling with a 2000 Tacoma Prerunner with the 3.4

 

Yes I know the thread is two months old... have you purchased a trailer yet?

http://www.northwoodmfg.com/17VS.htm

Well to put it in perspective, check the specs on the above trailer (17VS Hardwall). My buddy across the street just bought an 08 F-250 Superduty because his 05 F-150 struggled with the 17VS (hardwall) trailer. Its dry weight is less and the GVWR is only 180 lbs more than the one you're considering for your 4Runner. I wouldn't even dare to pull his trailer with mine.

 

I pull my 24ft fisher pontoon in the spring and fall to put in ky lake with my 96.

 

pulled the same trailer down from washinton to denver about 1200 miles and i pulled it at 70 to 85 except for hills had to drop down to about 45miles an hour. trailer had aprox 5000lbs in it had a tongue wieght of aprox 160 to 180 im guessing on that its all that i could lift cause it didnt have a jack on the dang uhaul.

i would actually say your swerving problems where more related to either not enough tongue wieght or improper loading.

 

Bought an 07 TrailCruiser 26-SB (26 ft camper with a 5ft rear slide). Dry weight is 4011lbs. No real problems, except I was over heating in the mountains. Cme to find out all 4 wheels on the camperlooked like this, / \ .
There is either a design flaw with the torsion axles they use or the mounts on the camper frame are out of lne with one another.

When we first looked at it, I told the dealer that the wheels looked bent on the passenger side. He said they had to order new axles because they were damaged in delivery. Waited 2 weeks for them to come in. They installed them and off we went for our 1st camping trip with a camper. Camp ground was only 10 miles from my house and 35 from camper dealer. Anyway, got to the camp ground and noticed that the wheels looked a little funny. Thought just the way its sitting. Camping trip over, and took back to dealer for some other small issues. Picked it up a couple weeks later for another trip to the same place. Noticed the same wheel problem, but now both sides looked a little cocked. Still no concern. Left 3 days later for a 170 mile, 4 day camping trip, one way, into the mountains of WV. Overheated twice on the way up but arrived at camp site and noticed that now they really sat out quite a bit. Left camp ground at end of trip and headed for home with a planned stop at the camper dealer. Overheated 3 times on the way home. We get to the camper dealer and he notices the camber of the wheels as soon as I told him I have a problem. ALso, found out that the rear drivers side tire on the camper was starting to peel away. It had chucks of rubber falling off the inside.

He said there is a problem and they would have to contact the manufacturer. Still waiting on a response, but only been 4 days.
While we were there I noticed that all the 08's had gone back to the leaf spring set up. When I asked, he said that he noticed that too and would inquire as to why.

I think the manufacturer found a design flaw in using the torsion axle set up and has since returned to the leaf spring set up. I did tell them that since it was only 1 1/2 months old, I would not accept it if there had to be any cutting and welding done.

Now, I'm just sitting and waiting for a reply and

 

Sounds like my trailer. Shadow Cruiser 189FBR. My 04 d-cab Taco tows it with no problems, only mods are a trans cooler, suspension mods and Tundra front brakes. The biggest advice I'll offer is to take your time when towing, my rig is totally stable up to 60-65. Any faster and it gets a little scary. And the gas mileage goes from bad to really bad if I try to cruise at 70.