I tow with an audi A4 allroad quattro, absolutely no problem at all with my Baycruiser 23, and it returns about 40 mpg (maybe a tad under) on a steady run which is pretty good I think. Maybe I am just about at the top end of towing weight for this vehicle, bearing in mind the 80 percent rule.
Julian, my neighbour has a Yeti, and like you we live in a hilly area - where four wheel drive is essential in the winter, and they have no problem at all in the snow and icy roads that never, ever see a snow plough or gritter - though the council were kind enough to put a box containing salt/grit about a mile away, but you have to use your own shovel and barrow!
Andy