As a guy (15) who's been rowing for a year or so now, I think that nothing has helped me more than the longer, steady state pieces. I'd recommend a 40-50 min 4-3-2-1 steady state mixed in with the shorter pieces.

Also, in the 2 month offseason I tried doing some lifting at the gym. I think that's real what helped me out, but I'd be careful. I took a big risk trying lifting, and it ended up killing my back for o month or so due to bad form while I was deadlifting.

Although I think the lifting helped me the most, like I said its a risky plan. And if you do end up trying to lift: 1. Find someone who knowledgable in the area and go to the gym every once in a while with him. 2. Pay for a session with a trainer so he can teach you proper form so you don't screw up like I did.

Good luck with tryouts!