I have had a recent opportunity to test my EC-21 in what is considered "rough water" on an inland lake in NYS, named Seneca. Seneca is 42 miles long, 2 to 3 miles wide and oriented almost exactly N and S. When the wind comes out of the N for a few hours it can build up to a closely stacked 2 to 4 foot chop.
The EC-21 seemed OK, a little wet but the pilot house is cozy and dry. I did remind myself that I was in a 21 foot, essentially open, boat. Taking the chop on the beam ends is not good, but she does not roll as bad as other boats I have had, including a Horizon Cat sailboat which has a very similar hull shape. The Yanmar 30 is plenty of power and the boat is very nimble and turns on the proverbial dime.
All in all, I feel that the EC-21 is fine for the inland lakes where I will use her for fishing and day trips, but I would be especially interested in the weather forecast should I launch in Lake Ontario, which is more like an inland sea.
As we all know there are old mariners, and there are bold mariners, but no old,bold mariners.
I know this discussion has been had many times on this thread, but I am a little concerned about the low freeboard and the possibility of a load of water in the cockpit with only a tiny bilge pump to the rescue. I wish the EC-21 was designed with a self bailing cockpit.