I've been sailing upwind with one rudder one on many races for approx 10 years. I raise the rudder from single trap and higher winds. In lighter winds you need all the rudder area you can get!

Step by step
1. Your sailing with double trapped full power with one rudder.
2. Luff the boat gently and jump in from the trapeze when you are heading directly into the wind.
3. Crew jumps over to new side.
4. Skipper pops down the rudder, releases a bit of main sheet and jumps to the new side. Since the skipper is slow over to the new side because of the rudder you get the benefit of a roll tack also.
5. Gain speed on the new tack with both rudders and start sheeting in the main.

Now you have two options
Option 1
6. Gain some more speed so you can sheet the main in a bit more.
7. Raise the rudder
8. Go out in trapeze.
option 2
6. Go out in trapeze and sheet in the main for max power with both rudders.
7. Go further back in the trapeze and kick the tiller up with your rear foot to release the kick up.
8. Kneel in (stil in trapeze) and pull the last bit of rudder up to locked position.

/hakan