score:4
Is not too long as to stick out the sides of the RV (7'6''?)
I am not sure what you mean by this, because - except for very few motocross bikes, you can't lift and place a bike on the back of the RV. Please consider renting a motorcycle trailer; if you will be doing so - you may want to invest in a tarp or similar to protect the bike from the elements.
Now, as to your bike choice, for comfortable 2-up riding, you'll need a tourer-class bike, personally I would recommend a sport-tourer or similar.
These will have a slightly upright riding position. If you will be traversing paved roads, these bikes will be a great joy.
If you plan to go off-track or will be going up any kind of unpaved road or trek/trail - then I recommend a bike like with a bit more tracking and road clearance. Something like a Motto Guzzi Stelvio or similar.
Please note - riding a motorcycle on mountains and curved roads with a steep grade requires significant rider experience. If you are unfamiliar with the bike or the terrain, I would highly recommend renting it well in advance to familiarize yourself (and your passenger) with the bike.