yeah Jesper is the man
as far as i know they are symetrical
they gybe pretty well as long as you have enough fin in the water
depending on the tail width of the board.
do you intend using the 23 on the jp45 (i think that is what you where using?)
i found the 21 on my manta54 with a 7.0 on the swan very acceptable..it was slightly underfinned but still very manageable and nice to sail..
if you are using it on the jp, the 19 or 21 would be fine.
as for the ka's well
we i have given up waiting for them here
in wa