I'm not sure I understand the question 100% but I fitted an elliptical rudder to my SF.
The rudder as delivered didn't fit perfectly; the section in front of the pin would impact with hull as I swung it from side to side. So I had to file the material down a bit. Took a couple of minutes and then it worked perfectly.
I have two elliptical rudders - one is similar to but a little smaller than the Epic V10 rudder. This one I find a little too powerful for the SF - when traveling at speed down the face of a wave, if you kick the rudder too hard, the boat almost leaps out of the water!
The second is from Fenn themselves. It's a lot smaller and narrower in profile. In my opinion the profile is too narrow and leads to the rudder stalling.
So I'm looking for a compromise - something of the same shape as the bigger rudder (which I got from Orka paddles here in Cape Town) but cut down a little so that it's slightly bigger than the Fenn rudder (and has a meatier profile).
Rob
Currently Epic V10 Elite, Epic V10 Double.
Previously: Swordfish S, Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...