Most places like hobby shops and craft stores stock Mid West balsa, it's stiff and heavy. Very stiff and heavy. I have bought sticks for trailing edges and my GP slot cutter wouldn't go through it. They also have tapered stock for ailerons and elevators and we bought that hard balsa just because of that. Some of the kits and ARFs used very light weight wood for these and they would flex so we often changed them out for the Mid West wood. Wood dealers usually stock 4 different grades of wood but I found just stocking the contest grade works well for me.
It's been a long time sense I built the SSE and I didn't recall it as having a counter weighted rudder, it looks good and that rudder looks very strong, good design!!