I have used F4 fins in my iSonic 117 from which used to be the iSonic 121.
The D2 is a great fin when power up they are easy to control and no sping outs. I have tested all sizes and rakes in this fins thru the last 3 years. I think these fins are underrated by the consumer here. They are faster, more slippery and good quality. I have never broken one of the F4 fins and I have used them in all of my boards including my formula boards. But the slalom D2 is one of my favorite fins when the conditions are power up. Just buy a size up Example in the case of a 44cm buy then a 45cm.
I can also recommend Vector fins specially the Canefire in carbon. This fins are among the best and many PWA riders used them. This are the fins I mostly use and Jeff the owner always can help in the selectionby the experience of his team riders.