You'll easily hit 1000 pounds with everything you add including a full tank of water, clothes, food, chairs, propane, battery, A/C.  The last few things are usually not included in the sticker weight on the pod (the A/C will be included if it was factory installed, but not if it is was added by the dealer).

80% is a good figure, though.   

I fear you fail to count the cargo you carry in the truck as tow weight. The words "tow capacity" dont mean that as long as the weight isnt in the actual trailer being towed, dont count it. Everything you have in the vehicle, or trailer, including you driving, is cargo. 

One thing that I'd add to this thread, is that with many R-Podders, they started with an existing vehicle, or have aimed for one that tows securely, but once unhitched, is easy to live with around town or for trips "to grandma's house" etc. (Plus, the other common drivers may be a wife, daughter or young son).

This URL will take you to an excellent page with a calculator and some explanations of towing capacity.

http://changingears.com/rv-sec-calc-trailer-weight-tt.shtml

 If you tow max trailer weight assume 10% tongue is safe (can't find max tongue on the 4Runner receiver, but it might be 500lbs because the stock receiver is a rear cross member mounted one, not a frame mounted one.) Frame mounted OE receiver (was available for the V8 and can be mounted to the V6) has higher tongue capacity, but the tow capacity weight would be the same.

 If you go to the MAX, your 5 speed will become a 4 speed. Forget about using 5th. It won't happen even at 55 mph. It will CONSTANTLY hunt 4th-5th if you try. Leave it in 4th and accept how it behaves. You will never break any 0-55 mph speed records towing 5000 pounds. It will take a solid 20+ seconds to get to highway speeds when near max tow capacity. 

 I know these things because I had a 2003 4runner V6 (4 speed). It did not like a 2013 Starcraft 17RD, and it also did not like the 2013 177 R-Pod. 3rd gear was the norm, MAX speed was 65 mph on the flat at about 3000 rpm...period...Or if trying for 70 mph, wringing the engine out to near 3500-4000 rpm all the time.

 After 12 months of small trailer ownership and about ten 480 mile round trips, I realized I needed better, and stepped up to a diesel. No reasonable comparison between my soft roader VW Touareg TDI and the off road designed 4Runner. I loved my 4Runner (10 years, I bought it new) but it was NOT a good tow vehicle, and it was NOT fuel efficient under any circumstances. No regrets. Even VW dieselgate won't really hurt me. It's sad about the whole dieselgate scandal, but VW deserves an EPA boot up it's ass for the lying.