Advice Needed for Winter Training

I am a heavyweight rower trying to get a sub 7 for my next 2k for the spring, or maybe even C.R.A.S.H.-B's. Last spring, I was at a 7:09 2k, but have gotten about 20 seconds slower. I was wondering what workouts I could do over the winter to efficiently get me there. I've heard steady state is good, but I'm not sure how long and what pressure.