Re: Question about sail area
Chiko you are on the right track :-) I don't know if you realize how lucky you are to have gotten Bob interested, but I think he will have some very constructive suggestions.
I'll just give you my opinion on what you specifically mentioned: the boat in my avatar is my old boat, SA/D around 12-13, long shallow full keel. She was fun, and tracked great, but slow and hard to maneuver especially astern. I sold her and got a much more modern centerboarder with a planing hull and SA/D in the low 20s (depending on crew) - going fast is a blast. In a second I would tell you make the main/fore area as big as possible (and plan for reef points in the main), and go with as high-aspect-ratio and deep a keel (and rudder) as you possibly can.
Other notes: first, get your transom above the waterline a bit. You want a clean exit; what you have now will create a lot of drag. Second, it looks like your LOA is 12 feet, but you're adding a sprit. I don't know about your budget or planned construction methods, but if you can skip the sprit and bring the LOA up, there is no substitute for waterline.