The Seal 850 which shares the hull moulding of the 28 has always had a Super-Seal 26 rudder mounted on the transom. Also some 28 owners have adapted to Wheel Steering with a rudder mounted on the transom. There would therefore not seem to be any good reason not to have the rudder there where the leverage must be much better than the forward position dictated by having the rudder post in the centre cockpit. You would have to have wheel steering or some kind of whipstaff arrangement to get control from the centre cockpit to the transom.
A number of members have had trouble with the standard rudder arrangements - especially the earlier ones with a retractable plate lifting into a fibreglass housing.
Geoff Harwood