Most sailboat design principal relates to mono's not cats and if adopted can put you out by a significant amount.

It's been my experience that for good balance, the CoE in the sail configuration should be directly over the CoLR, which in cats is most likely at the dagger boards. Variations in mast rake will effect this position.

I think a good test would be to put an existing boat in the water without a rig or rudders, with boards down and apply a lateral force at the c/l of the boards. I plan to do this next time the boat goes in the water.

When I designed the 430, I opted for a mid position between the hull CoLR without foils and the CoE in the rig. The boards could be further back.