I have just bought my second set of H4 fins to ensure I have them on both my bigger wave performance boards. I originally bought a set for my down the line 7'3" gun as the speed and power for late drop, large wave conditions is unparalleled.
I then switched them to my 6'6" mid to large wave rounded pin allrounder and found that turns and power through cutbacks and bottom turns was excellent.
So I had to keep the first set on that board and buy a new set for the gun!!
Woohoo! Love 'em.