I am considering upgrading the old 85L wave board to a slightly larger 93L quad or thruster. It sounds like the multi fin boards have a real advantage in larger sizes. The only thing I am worried about is it seems like the multi fin setup would act like rake picking up every bit of weed in the weedy location I sail. Is the smaller finned quad setup better than the single fin thruster for staying off the weed?

I run weed fins in both my quad and thruster, the thruster is less likely to grab weed and I feel less drag with the thruster. You really know when you hit heavy weed with a quad, it's like putting the brakes on hard. I prefer to run my quad as a twin in weed with my twin weedies as it gives less drag and behaves nicely in heavy weed, I do sail in what I'd call extreme weedy conditions.