The load from the sails on a schooner rig increases lee helm the further apart they are, as the front rig does more work/has more sheet loads.
There needs to be enough foil in the water to resist leeway, which is solely a function of sail area and hull shape, not rig location. If the rudders are smaller than this, there needs to be a board or keel. If the rudders are large enough and both are going to be used it doesn't matter how close to the ends they are, apart from non sailing reasons. Some of these are access, tiller length and hull strength.
I like rudders on the beams for safety and ease of construction, and the beams close together to minimise water drag, tensioning the tramp and reducing the length of hull that needs reinforcing. So everything is related, and not always just to optimise the sailing performance.
There are a few generalities in the above, but it pretty much conveys my experience with the schooner rig in El. The owner of the KSS El is putting 3 mast steps in his boat, so we may get some feedback on schooners in the bigger sizes.
rob
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