I use a double with my solo, its a 240 I believe. I have not personally used a Pack, and I'm not familiar with the Kaynoe setup, but virtually everyone I've spoken to who has used them lowered the seats for stability. I have the seats in my Mohawk at their lowest setting.
As far as going up or floating down, it depends. You lose some fishing time going up, but its often the only way. It depends a lot on the shuttle, which can be many times the float distance. You also half to be prepared to secure you craft at the take out. That can be tough because while people won't saw through a bicycle frame, a little plastic or wood doesn't offer much protection.