thanks chaps – really not sure how I managed to miss that article!
Having read this, am I right to conclude that the issue here is that a simple drum and swivel system without the furling spar is unstable when sailing partially furled? I’d be interested to know how likely this upper genoa unfurling is to occur in practice. I hadn’t really appreciated that the drum and swivels are really just a quick and convenient way of getting the jib/genoa out of the way completely (which is still very handy when dealing with kids who may be choosing launching and landing times for a spot of intense family dynamics)
I’ll need to chew this over since I can’t really afford this very expensive bit of kit just now! I can see that when cruising there is an option to swap sails reasonably easily, and on our club reservoir situation you can pick your sail to suit the situation before setting out.