Stavanger, Tuesday
Guy, I bet your gaffrigged catboat would do very well with a junk sail. The most noticable difference will be that you will handle changing wind conditions much, much more easily. Maybe you will need a little, simple jigger to balance out the sail, or maybe not. The problem may be to get room for sheeting. One method is to use double port-sb. sheeting. The other is to sheet the sail to a retractable boomkin.
If you go to "my" folder here:
http://www.junkrigassociation.org/arne
you may find stuff of interest.
What about skimming through "Junk Rig for Beginners"...
.. or " A white sail for Edmond Dantes..." part 1 and 2
These sails are easy to make and with the shown camber, they will ensure good upwind performance.
Anyway, good luck! Arne