One of the LAST boats I would want to be on is an IP in higher winds......but that is me.
200 years of yacht Architects would vehemently disagree with you. The IP is not as wide as most big cruisers, and coupled with the full keel tends to make the hull less stiff. As we all know the lower the stiffness, the better the rough water capability.
The huge keel mass coupled with the heavy hull results in a quite low CG further enhancing its rough water capability. And as everyone knows the IP is extremely respected in its rough water capability.