ORIGINAL: Rebel bay
For more reactivity and stability, I prefer when the rudder is behind the propeller(s). Hull is 1 meter, stingers are 10cm + propeller and distance between the hull and the blade is 15cm
That might be the case on monos but most cats i know it makes no difference wether the rudder is behind the props or close to the transom in fact many seem to run better with it closer.
Matt that set you showed should work fine if you remove the strut and just use the rudder.You do not need a long standoff rudder on a cat,level with props is plenty.