Since this thread is getting updated I should give an update on my surfski progress.
*I gave up on the Epic v12 and got a Stellar SR 2g, which felt downright easy after struggling with the v12. I was quite comfortable in rough water and downwinds on the SR once I got my seat pads and such worked out.
*After a few months of that, an opportunity came along to trade the Stellar SR 2g for a Stellar SEI 1g. I took it, because I was looking for more top-end to help me keep up with the good guys in flat water.
*I feel comfortable on the SEI 1g in terms of balance, and recently got a 13.4 kph average 10 km downwind run on it.
www.strava.com/activities/1995066575
*I think compared to the SR 2g the SEI 1g is less tolerant of funny angles and maneuvers when downwinding. For example, if I drift just a few degrees off of perpendicular to the wave crest on a run then no amount of rudder or paddle dragging seems to bring it back. I'm not sure how much of that is the SR vs. the SEI, and how much is the 2g vs 1g, and how much is just a thing that all displacement-nosed craft are prone to do on a wave ride.
*I'm using the standard 8" stellar rudder. Maybe a surf rudder would help, as others have suggested.
*I gather that some of the newer generation skis have a little different rocker profile and rudder and cockpit position to make them more forgiving and maneuverable for their length.
Anyway my new take on surfski is: Yes, it's hard, but if you start with an easy boat like you're supposed to it's not so bad, and boat design seems to be slowly evolving to be a little more user friendly, at least for beginner / intermediate boats.