If you still have a mainsheet track fitted then that is more than adequate to secure a line to the mooring buoy.
If you have done away with that and are using a bridle then consider fitting a timber section where the track would have been – an example here;
http://wayfarer.org.uk/index.php?option=com_content&task=view&id=203&Itemid=140
Fitting the cover from the boat whilst afloat sounds like an interesting exercise.