Thanks for the reply. I checked out the MCF fins and their largest is a 38. Most of my sailing on the iS111 will be free riding blasting and so far, my expeience with the 38cm Drake fin that came with the board is that it is too small for my style of sailing.
Last time out I was on the Drake 44 on my 7.4 sail in variable winds up to 20 knots. The 44 didn't seem too big in the 20 knot gusts. I probably won't invest in more than one good fin and what I want is something that will work best with the 7.4 in choppy conditions. The Tectonics Gold Wing seems like a good option and they will make any size I want. I will have to look into Vector.
I know what the Deboichet fins go for in formula sizes, but what do the slalom fins cost in US dollors?