Les,
Most Dumas set ups have only about 12 pounds of ballast. That is not enough for 13 mph, which is borderline for most skippers in an A rig.
The assumption is the sails are wing on wing (A must), the leech is tight and the boat is balanced for the conditions (mast position, ballast and sheet postion).
What I hear indicates the boat is over powered in the conditions. Sometimes, for certain boats, this cannot be corrected. There is a point where the skipper needs to move to a B rig.
An EC12 fully sheeted out with a tight rig and the mast forward for the higher wind should not "Rock and Roll." It may fall off the sailing line but not rock. That is a sign of being out of balance.
A boat that is overpowered, having done the right things, will broach. A boat that has all the tuning above correct and has a strong rudder servo and the skipper a steady soft thumb on the helm will broach straight ahead, bury the bow to the mast, come to a dead stop then the bow will rise out of the water and sail on.
Lastly, the skipper has to decide when it is time to change rigs or withdraw. In my opinion, RD's stop an event long before needed and hence many do not get the experience of dealing with the conditions. The safety issue considered should mainly be for the experience level of the fleet and damage comes from out of control boats...the EC12 is capable of sailing in heavier air than many think.
I hope this helps. Practice heavy air sailing and these things will come. In an event a skipper's prime concideration should be the safety of other boats by the actions of yours. Sailing close to others in a high wind is very high risk. The people next to you are your friends.
...94