i strongly agree with the fitness component

like a chain, your only as strong as the weakest link(or links)

i BECAME a solotripper because the 3 guys who i used to go with waited all year and decided to get in "shape" on the trips

that put a crimp in the travel plans year after year and made me the bad guy because i didn't want to spend the trip basecamping and partying!!
your goals and expectations should all be worked out pre-trip and the difficulty of the route chosen can be discussed!
While it's true that the weather conditions can make portages more difficult, it's still a good rule of thumb, that the longer portage the harder??
i know there are many exceptions to this but if you can't carry a pack or canoe a football field length at home then your going to be sucking wind on most portages i've been on!
It's not a prerequisite that everyone is in tip-top shape but it's nice if your all close to same level, whatever that may be??
Being the only fit person means YOU end up picking up the slack for your friends and that get's OLD real fast