Yeah, it will do fine with 3500 pounds.
Beware wind drag eats more power than trailer wight. And round trailers like the R-Pod aren't always better, because they increase the gap between the tow rig and trailer, which affects drag more than the shape of the trailer. Of course, total frontal area matters the most.
The reason the Highland isn't great for towing is because it makes its torque (and therefore HP) at a pretty high RPM. You won't be able to tow even a modest trailer in 8th or 7th. If you head into a strong winds, you might even be cruising in 4th or 5th. The motor is so smooth that alone probably won't be offensive, but it will be noticeable and it will cause it suck fuel. With with a 17-foot RPod, your fuel economy will only be the same as full size trucks puling much bigger trailers.
The issues isn't isolated to your Highlander. It affects all small-displacement non-turbo V6s. Even the 1/2-ton pickups. They make good power, just need to spin to make it. The 8-speed auto will ensure you'll always have enough HP, but it's history for towing is unknown so far.
