Originally Posted by Cold Butt Stephen
It'll work out fine and your friends will see the greatness of hammocks at some point. As far as the ridgeline, I have heard that the rule of thumb is 83% of the length of the hammock (very specific, I know). If I were you, I would go to the park/ backyard/ wherever and try out different lengths to figure out what you like. There's also no ridgeline police, so if you decide you just like it better without it then scrap the ridgeline, at least for this trip.
I recently made a set of whoopies and straps suspension in addition to an adjustable ridgeline that included a fixed end and a whoopie end. It works great!