I was able to use the Walu weedfins, 15/9 on my Goya Quad 84 in early June. The weed conditions were very heavy, with large patches of weeds (sort of a long, thin grass). Wind was about 20 mph and I was on a 4.7. The fins worked very well at clearing weeds. I then switched to my small board JP 74 Quad with the Maui Ultra weedfins (14.5/9) as the wind picked up to 22 mph, and noticed that the MU fins (these are the X fins series) did not clear as quickly as your fins, so I’d have to say in a side by side comparison, your fins do work better in heavy weed conditions. I also noticed your fins felt more lively and springy, a nice feeling in the waves. I did not have any problem staying upwind with your fins. I want to try the 16 cm fins with my 5.3, and will let you know how that works out.