The dagger board needs to be set reasonably close to the middle of the boat to achieve that condition with a single board.  On the 18m proa, with its single central dagger board, it is possible to get close to balance without using the small rudders at the ends by letting the board swing aft a little although it was only intended to operate vertically.  

If the dagger boards/rudders are located more toward the ends then the best result is achieved with both rudders down when on the wind.  There could be a slight penalty due extra wetted surface.  This could be determined doing the analysis.  That reduces the size of the rudders as well.

Off the wind the leading rudder could be angled horizontally so it is out of the water.  There may be benefit in also angling the trailing rudder to have less drag. But again that needs to be analysed.

From our experience with the central daggerboard on the 18m proa, we always swing it down at low speed (less than 6knots) and lift up at any speed providing we are on port tack.  The dagger board is only parked one way although it can swing both ways to some degree.  I expect that lifting Campaen rudders could be done at any speed but lowering probably requires being near stopped.

From a practical perspective it is probably better to design to have both boards down when on the wind.  In my view shunting is tedious enough without having to lift and lower boards each shunt.  Maybe crank on the aft one to almost eliminate the weather helm then use the front one to steer.  The best speed is achieved when the boards produce all the lateral restraint rather than having any leeway with the hull.  The long shallow hulls are inefficient at generating lateral resistance so drag goes up considerably when pushed sideways.