This year things are a bit different from previous years. The good weed is thicker after 3 years of good growth and there is now a lot of Algae type (snot weed) in the lake. The former makes more drag than previous years which is not really an issue, but the snot weed foats a bit and sticks to the fin when trying to start.
So this year I have had to go to 50 degree type weeds, rather than the usual 35-40 degree types I have always used in the past.
45 degree type fins still work OK as long as they are less than about 23 cm, and you try to avoid stopping in the thickest weed. The Tribal Weedspeed's and Extreme Weed's work OK in the latter category in under 23cm sizes. Over that you are getting a fair bit of drag in the thick weed in the shallower glassy areas.
The 3 fins I have been using most this year or a Black Project WeedSpeed 50, 25 (20 cm deep), a 21cm Techtonics Weed Demon (50 degrees), and in the speed board, a Chocko modified (raked back to 50 degrees) Curtis 17cm.
Early season I had good results with the 21cm Tribal Weedspeed (40-45 degrees) in the JP SL 70, but it does not suit the new IS80 quite as well.
The other reason the shorter fins are great is that you can feel more confident going into the really glassy stuff where it is only knee deep or less.

PS. You probably need to do it in the next couple of weeks if you want to sail the SE winds. They usually tend to disappear by mid to late March. But it can still be really good on the SW fronts through Autumn and Early Winter. They just are a bit shorter in duration, but often much stronger.