With wings, long span with narrow chord are more efficient (lift vs drag), so a deep, narrow chord rudder would be good for racing. But the same area oriented horizontally (that is, a shallow, wide chord rudder) will work much better for sculling. So, the question becomes: is your sailing pond beset by calm, fluky winds =>sculling rudder to get you home , or are you more interested in racing =>efficient rudder?
I put the sculling type rudder on my square riggers as I find myself sculling more often than racing
. My ships already move faster than scale speeds, so I don't usually need the greater efficiency of a racing rudder.
Rudder swing of 45deg to either side of neutral should be sufficient. This is within the normal servo arc, and will be achieved at the rudder if the servo arm and rudder arm have equal lengths.