Re: Do I need a guy and a sheet on each side of spinnaker?
Our spinnakers most often go up with a jib up, unless we're going straight into a spinnaker run, then we'll hoist it just with a main up. So no, it's not necessary on any sized boat...
It's definitely easier to hoist the spinn in the lee of other sails, esp as the wind increases.
Definitely don't recommend flying spinnaker only... very difficult to douse if the wind pipes up unexpectedly, and tough even if it doesn't.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"