The sub floor on my Islander was actually glassed to the hull under the settees and screwed to the ribs. I had to remove the settees (which I rebuilt) to get the floor out. This is a tough job as the sub floor was installed, on my Islander anyway, before all the remaining interior and bulkheads. I ended up gutting the boat and doing a complete refit.
Great sailing boats the Islander so it was well worth the time and education.
A people that values its privileges above it's principles will soon lose both.