I have sailed with one rudder on the upwind for many years and I start doing it from single trapeze and up. I seldom start with one rudder, it's to easy to stall if you get disturbed air. During the tack you don't lose much when going into the tack since you do a "roll tack" by spending time getting the rudder down. But you lose a bit when you start sheeting in on the new tack because you have to gain speed until you can raise the rudder. The option is to jump out in trapeze with both rudders in the water and then kick the rudder up with your rear foot and lean in and get it up from the water.

Another advantage is that you can trim the rudders close to parallell to optimize for the downwind and keep both rudders in the water on the downwind. I have capsized a couple of times trying to get the rudder down before the gybe!

/hakan