After 6 months experimenting, I think I am now at my final configuration which allows me to sail with the main boom parallel on all rigs.  Through my whole dinghy sailing career I wanted to sail with the main boom parallel to the deck.  It looks right and usually fast.  Mast rake is up to 2 degrees and my challenge was getting a fin in the right position to work with this rig.  

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The goal was to sail with a perfectly balanced boat with a hint of lee helm so when I am looking for wind shifts, the boat is sailing as fast as it can upwind.  With the previous weather helm I had tended to lose speed when I looked up the course.

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I am using a Craig Smith fin with a Robot bulb. 

 

Fin

Leading edge of top of fin to line perpendicular from bow (excluding the bumper).  500mm (measured parallel to the waterline).

Fin leading edge is exactly 88 degrees to waterline (tiny rake)  I had got this to vertical but the boat was not quite balanced right.

Bulb angle to waterline 2 degrees.  Bottom of bulb is 2mm above max draft

Hull to top of bulb down leading edge of fin.  330mm

Bow to tip of fin where it enters bulb 640mm.

C of G of bulb is 5mm forward of leading edge of fin

 

Fin weight.  I can't give you the exact weight but it is lighter than anything I have seen.

 

Rudder

Depth of rudder 220.  very thin chord but no experience of stalling

 

Rig

Top of boom band to step 135mm

A rig mast rake  1040  (bow behind bumper to 900 mm mark on mast measured from top of foredeck.)

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My next step is to work up a set of sails for open water.  More on that as the summer progresses assuming we eventually get summer weather.