Trouble applying bezier curve splines and using with curviloft skin contours

Hello community, I am learning use of spline curves to create a hull model of my boat. I have drawn the major curves from the deck down, none of the bezier tools seem to easily apply a simple curve with start, end and a single point. haven’t found a good explanation. I have also been unable to apply fully apply curviloft. Trying to apply skin contours, but have trouble fully skinning, have checked for edge voids etc, but no luck. often get a sketchup error “Contours cannot be interpreted correctly. Try to force separations with small cut lines. Empty the selection?

SO410 - Hull Loft 1.5.skp (2.0 MB)

It is recommended that the number of segments for each curve be the same.