Don't have any experiance myself but remember talking to Paul after Kath and he ran theirs up the French canals for nearly a week at 6 knots.
I remember he was impressed with how well it coped, and only gave a slight cough and splutter when opened up again at St Malo.
RIBBED For extra pleasure.
Member of the ebay Blue RIB cover club.
Member of the Bombard 380 Aerotec club