Where are you located.
You should be able to get the Tangent Fins at Southport Rigging in the Kenosha WI area.
The guy that designed the Tangent Fins has been working at Southport for a couple of years.
I actually worked with Bill K. and Curtis H. on the Someweeds way back when.
They are pretty good, but I could never talk Curtis into going with the vario rake LE.
I manged to talk Chuck Ames into some Vario Rake SB Weeds and they were quite good.
The SB Weeds work well on formula boards.
The Tangent 46 would be very good also. Might get away with a 42 if you are not racing and not spending all your time looking for the highest upwind angle.
Wish you could try a Lessacher Design 40 cm Formula Duo.
If you are ever in Hatteras, look me up and you can try mine (if your board accepts Deep Tuttle).
They shed weeds really well, but the duo foil system helps with spinout and shedding both.
Hope this helps,