Yes, I've never put a lot of effort in trying different fins on my IS122. I should have.
6.7 is also my preferred sail on the IS101(97). I sometimes use a 7.8 on it when the water state gets too rough for my IS122, but the 7.8 only works well on the IS101 with a lot of wind. I need so much wind that often the 6.7 also goes. On a speed strip, the IS101 is perfect with the 7.8.
IS87 / IS101 / RRD114 / US147