Well I don’t want to recreate the wheel here as there are already numerous articles on this. However I recently found a pretty good one link. It’s a bit technical but easy enough to understand.
I resumed below some of the key elements of foil design :
Its, length, its thickness, its shape, its width and one final major contributor to its performance is the location of this maximum thickness.
On our 1 metre we have 2 appendices. The rudder and the fin keel
Personally I found Craig’s parallel rudder an excellent design. And it works very well with my TS2. Craig’s original rudder was good but I found that his new parallel one brings that much more speed downwind while retaining good upwind speed. Furthermore I know for fact that lots of other sailors also use his rudder on other boats and it also turns out to be successful.
Of a similar design but I didn’t test it is stealth rudder. Similar to Craig’s one but more rectangular. It’s seems to be working very well on Stealth boats but I don’t really know how it performs with other boats.
The Fin Keel
I also like Craig’s original fin and the theory behind. However I was told that I would gain more speed with the new parallel fin but the key is to find it as it is trickier to get that extra speed. I would say it’s more of a personal view than a true performance difference.
I have also heard that Dave Creed (hope I spell his name correctly, if not I apologise) makes really good ones too.
Personally I would seek advice from the boat designer as he would have had to “play” with few designs or at least take the design into consideration during the design and test phases.
In any case it is important to remember that these different shape of fins will only contribute to a minute portion of your overall performance. Pursuing the constant chase to the best equipment shouldn’t be your focus but tuning your boat to the conditions, having a good start, and making the right calls will have a more significant impact on your results.
My view : start with proven equipments (so you can’t blame it on the material), and learn how to get the most out of it. Review what worked out well for you in each particular sailing conditions and what didn’t.
More often than not the boat can do it but the biggest learning is on the skipper.