No problems Joe if you have any questions on sailing the Serenity just ask as I love this board and have many enjoyable days sailing it both cruising up the coast and doing race training. It is such a good physical work out.
I do not have the luxury of another fin other than the ones supplied with the board and will be interested to find out how you get on with the 64 cm. The small fin does come in handy if the wind picks up after I have done a upwind session up the coast as I change over to it if I'm over powered for the down wind run.
In the video the shots of the board on the beach are with the small fin as there were waves so I tried it with that first but changed back to the 70 cm after 1 run. Unfortunately I did not get footage but by the end of the session I was having fun jibing onto the waves and riding down the line on the soft shoulder as the tide dropped. However I did not think about coming back in and it did cause some problems with the 70 cm fin. I am not very tall. When I went in the tide was high and there were no waves in the corner of the beach.
Roger. I am interested in your suggestion of a race fin but surely this will change the balance of the board a lot. As it will be at least 2-3 cm further back plus is much narrower and thiner. So I would like to hear the advantage of doing this over the small fin supplied.
Have fun on the water.