Skipper - I checked SCYC and they are booked through next May. After April I lose interest. Actually my preference would to see some of the Family Island Regatta the 3rd week of April.
1-2 night stays are all that are left even they are few and far between.
My guess is that there are probably many "regulars/repeat clients" that block out weeks years ahead. I guess there may be other accommodations on the island but having a boat rental is necessary for me and my fly rods!