Just curious, as the owner of a sweet, semi-vintage (1999) Subie, what year is your Forester? I understand that Subaru redesigned the Foresters at some point, not sure exactly when, to get better mileage, but at the expense of the towing power. I live in mountains myself, and know mine has plenty of oomph going up a steep grade, though I never have hitched her up to anything (yet).
I love the Subaru's AWD, though...it has really saved my "bacon" on more than one occasion on these treacherous, narrow roads and will probably do so again if the coming El Nino lives up to it's press!
Howling Wilderness, CA.