I have roughly cut out the floor, leaving a big margin for trimming. Tracing the shape, as described in the plans, is not straight forward as the sides are so wobbly. I am going to fit the seat brace before fixing the floor, with the hope that it will hold the whole thing a bit more solidly.
At the moment various bits are glued and curing overnight. If I get time in the morning I will fillet some corners and then take a break as I hope to go sailing over the weekend. Also need to fit the job in somehow.