Weed fin recomendation

[ducati]

Hi,
What size Weed fin would suit my old Starboard 186, which I use for 8-12kn only?
I run a 9m Sailworks Retro, am 85kg and normally run a 65 upright fin.
Looking at a True Ames Shallow Water Weed and trying to decide between the 44cm and the 51
I don't have a weed problem but sail in shallow water a lot.

Also What size would suit a Isonic 122 with a 7.5 sail?

http://www.trueames.com/wind_select...._id=14&Shallow Water Weed