1.) Everyone agrees that some weather helm helps boats performance to windward, therefor it is more efficient. Lets be clear about this we are probably talking about less than 1 % gain.
2.)This weather helm can be made so that it does not create a load on the tiller by balancing the rudder
3.) when the spinnaker goes up the centre of effort goes forward, so the weather helm will go, and can produce lee helm,
4.) Again a balanced rudder will make it so that you do not feel much of this load.
5.) having two centreboard slots will lose much more than any gain, since the only gain is removal of the lee helm downwind, and the loss due to this is microscopic. But the losses are:
turbulence from the slot:greater than 2%, slot gaskets work well with rotating c/boards, jam with daggers,
time taken to change boards, loss of at least 10 seconds each change,
Extra expense, you could spend the money elsewhere where it would make genuine gains.
