That's odd about the no vented notice. Mine is a
vented combo as well and came from the factory that way, but still the dryer cycle takes a long time despite it being vented. I think that's just the way it is as I've also seen other people saying that's their experience, so I only do laundry when I'm not in a hurry for it.
Sorry...I cannot answer your where to put the vent hole question. Our vent is a little to the left and down from the bathroom window of our 2000 Adventurer 37G, I think (can't see it from where I'm sitting in the stick house for a precise description--but it's in that vicinity). I agree that you should call Winnebago for their advice. Good luck!
~Lori