Thanks - I might try this out with just the trailer on a grassy hill to see if it makes a difference. But the bottom line for me is that I probably won't be using the Highlander to pull my boat OUT of the water anymore - the last thing I need is to get stuck pulling my boat out in the Fall on a cold empty boat ramp - I was lucky there was another truck to pull me out the last time. The boat ramp is close enough that I can drive a tractor over to pull the boat out - then hook it up to the Highlander to tow it to storage.
The Highlander has enough good qualities that I'm still satisfied with it - but the boat launch/traction control with no over-ride issue is a disappointment.
Just as a late followup to this - I tried the EV mode and it did not work out. First of all had to warm up the truck before EV mode would even engage, then it would disengage almost immediately upon pulling. This was on a grassy incline which matched the boat ramp. I ended up driving a tractor to the boat ramp to pull the trailer out.
The intrusive traction control bothers me - just the thought that this is an "SUV" that I'll have to drive like a front wheel drive, and I have to say that the dealer experience hasn't been great either. So I've soured a little on the car.
After going to the car show in Toronto last week, I decided to see about trading the HH towards something else. Current problem is that the market for used Toyota's is really terrible now - I was shocked at what the dealers were offering and even private sales look pretty soft. I knew it would be bad because of all the problems, but trust me - you would be shocked if you're trying to trade into another vehicle - even another Toyota.
So I'm keeping it because I'm not going to take that big a hit on a one year old car. Stuck in more ways than one...