BPF prototype Extreme Weed Speed fin

It is 21cm deep with a leading edge rake of 45 degrees. The area is 185cm2.
This is a fin for the guys who have proper speed boards and are going
over 40knots. It is optimised for about 45 knots but is efficient from
about 37 knots onward. It will need a skilled rider as it won't have
much grip below 20 knots.

I am just about to put an order in for some Black Project WEEDspeed fins, I have never used weed fins before and need to know if they are comparable in terms of size choice to normal slalom fins?
The pic on the site (blackprojecthawaii.com/ scroll down, the page isnt updated yet though) shows more area, especially at the base so I am guessing slightly smaller fin on the same sail.

I need them for the BSA slalom and know you guys use them a lot on your lakes. I will have sails from 8.8 - 8.0 - 7.3 - 6.6 - 6.0 - 5.5(dont think I will race in slalom for my first season if its 5.5 weather though!). The fins come in sizes 42,38,34,31,28. Ideally I only want to get 2, so which 2, but if I have to stretch to 3 then which 3. I have a full quiver of slalom and near full quiver of speed fins, but have read reports from previous years where the earlier events are plagued with weed.........

Thanks in advance

My new WEED Speed fin has arrived now I can go to lake George to see if I can improve my slow speeds