Today I attended a tour, organized by Hans Heupink for the Dutch Kayak Association. Due to the expected 7Beaufort-winds the planned surf-session was canceled and instead we made a nice tour in the Voordelta; to say hallo to a lonely seal. 
I did not take a testkayak with me today, but paddled Willem's Breeze (a clone from Plasmors' Ligue de Bretagne) a trustworthy kayak I did not use frequently yet. Given the wind 5-6Bft, I felt very secure in the stable kayak giving me plenty of opportunities to watch my companions.
Thus I noticed that Govert paddles his new Cetus. Having tested the Cetus myself, this was an opportunity for me to interview him and to record his experiences.
In fact his former experiences did not differ much from mine; written down on this website earlier.
First of all he was very happy with the stability, the great maneuverability, the responsiveness to edging and the big loading capacity.
Less positive he was about the new skeg-rope control because it requires too much force to operate it.
He also mentioned the bad habit of the Cetus to broach quickly in following, surfable, bigger waves.
At the end of the tour I asked him how it was in the following waves today. His experiences were a bit different , more positive, in today's smaller waves of approx. 50cm height. He mentioned he could, in these waves, anticipate well for broaching by just edging the kayak. It takes a moment, but than the kayak responds and kept course well. Probably, paddling in a following sea in a Cetus is something you have to learn.
If the Cetus will respond like that in bigger waves is the question.
I expect that edging in rough(er) conditions can help.
But because most kayaks responds well to their skegs in a following sea, I think that the skeg of the Cetus also is part of the issue. As her skeg is very flexible and because the high forces on the blade, while it works on preventing for broaching, it bends away sideways significantly. As a result, the effective surface of the bent skeg is reduced and while the skeg is a bit small already, I think that the explanation for the behavior in following waves can be found there.
So I think it is a good idea to experiment with a stiffer skegblade. Even better it would be if P&H increases the surface of the skegblade.