The benefit of removing submerged area with symmetrical rudders is not as great as lifting the asymmetric dagger board.  

The dagger board generates lift whether it is needed or not.  At low angles to true wind it does not produce enough lift to completely prevent leeway.  Somewhere between 60 to 70 degrees to true wind it begins producing too much lift so the boat has negative leeway.  This reduces speed over what can be achieved with no board.   Partially lifting the board to balance the sail heeling force reduces its efficiency so no point.  There is really no in between.  Board pinned down going to weather. Board up as soon as sheet is eased. 

The board as-built has a bit more camber than I had in the design so it allows higher pointing but is costing speed closer to 60 degrees to true than 70 degrees.  I did not want the benefit to be in a very narrow range as it could limit its usefulness.  Early indications are that VMG has improved by 30% with the cambered dagger board over just the rudders (20% better than the original higher aspect rudders).  This is consistent with the VPP I use for the proa.

With the two under hull rudders we tend to set the trailing rudder pulling us to windward to counter the weather helm and steer with the leading rudder around its in-line position.  If there is no cambered dagger board there has to be leeway because the CoE is well forward of the trailing rudder so forces balance to maintain course but leeway cannot be prevented.  This is the situation with a the "standard" harry configuration.  There could be benefit in having both rudders down when on the wind but as soon as sheet is free there is no point in having the leading rudder down.

The cambered dagger board in the middle of the boat can completely prevent leeway with high efficiency.  The board we are using has an aspect ratio of 4 and submerged span of almost 2m.  The section shape is a circular arc on the lifting side and flattish face in the pressure side.  Its AoA does not vary much so the edges only have a small radius.  This reduces tendency to vortex shed.  Bi-directional rudders need larger radius edges to give them a wider working range so the vortex shedding will be more severe.   

The new low aspect rudders are strong enough to support the lee hull and draft is reduced by 300mm.  They have same steering power as the original rudders being longer and thicker section but are less efficient due to the lower aspect.  They also have a top plate to close the gap to the round hull when off line so span efficiency stays high.  These smaller rudders work well in combination with the cambered dagger board. 

In my view the best combination for a harry is:

1. Schooner rig to enable CoE to be moved significantly.  (I have not yet sailed on one with this rig but it overcomes the issues I see with the Aerorig)

2. Flat sections in the lee hull with end rocker to get some dynamic lift.

3. Small 360 degree rudders in end of the lee hull forward of the crash bulkhead against the flat bottom to improve span efficiency.

4. Tilting dagger board with a side brace to take the lateral force.  

With the schooner rig there could be circumstances where the weather helm is neutralised by bringing the CoE forward and then tweaking both rudders to windward to counter leeway.  I have not considered this case in any detail.  The Aerorig no longer feathers safely if we shift the CoE forward so I do not regard it as a safe option.  Boat sails balanced on jib alone but the leading end of the boom has to be held to windward by other than the main sheet.  

Long answer to a simple question.

Rick