RE: min/max fin size for my isonics question for ian fox
Any fin sizing limits or formulae, even defining so called "min" and "max" sizes is always an aproximation because of the large number of significant variables outside our immediate control.
So, while a OFO rule -/+ 2 cm could be good for a waveboard, even a -10 /+2 cm is not totally correct for iSonics, especially the larger ones.
For your weight and choppy conditions, typically you could use
For the iS105 ;
32-34cm will be about the optimal minimum for 5.8/powered 6.7m.
36-38cm for mid-underpowered 6.7m and powered 7.8m
40-42cm for mid to light 7.8m
For iSonic 135 :
36-38cm typical 6.8m conditions(overpowered 6.8m use iS105)
38-40cm powered 7.8m
40-42cm typical 7.8m
42-44cm light 7.8m/powered 9.9m
44-48cm light 9.9m
For the higher wind, higher load fins, you will probably have more success with stiffer fins, whereas good quality fins in medium flex can offer some advantage in the mid to light range. The actual brand/model depends a lot on what is practically available in your local market. If you've the chance to meet with fellow surfers and try some "option" fins before you invest in new ones, that's also a good idea and gives you a better insight into different fins character and performance, which in turn helps you feel out further options and personal tuning as you progress.
Please let us know if you have any further questions.
Cheers ~ Ian