As the Sonotube has lines spiraling up the sides, I found a spare hour in an extremely busy weekend to cut out some styrene to attach to the dorsal fin backing and the tail fin backing. Construction adhesive works pretty good for that sort of thing although it is a big lumpy if you look close.
Tomorrow the shark will be painted with a new Rustoleum paint I found. It's textured multi color paint. Looks pretty interesting and I think it will be a good base for the fins and back.
Working out in the garage for an hour on Sunday night was a perfect end to an almost perfect weekend.