Hi DaniS,
OK you asked for it!
My first CA was a '08 SL58. Used it with Deboichet SL2 at first, but felt too sticky. Then I started using with Tectonics Falcon 32 and 34 (for 6.3, 7.0) and was much nicer, easier, looser.
In '09 I bought a 55 and was OK with same fins, smaller sails: the 32 with 5.9, 34 with 6.6. In '10 I got a 58 again, same fins but mostly 32 for 6.3, 34 for 7.0. With the '11 58 those same fins felt smallish and I used the 34 most of time, a few times also a 36 for 7.0. Now I have a '12 58. Started using with the Falcons, but even the 32 felt way too big (too much lift) for the 7.0! The '12 model has so much lift, I was never able to have a decent control on it using the soft Falcon fins. Now I have a 31 Vector carbon Rockit to test and I hope and believe that one will solve the control issue.
Medium wind, kind of the same. Started with a truly great '09 62 probably the board I loved the most. Mostly used it with a 38 Tomcat, with 7.0 and 7.6 (6.6 too at times); not much fin sensible, I'd say. Then I got a set of Talons and was OK with the 40.
The '10 SL66 was very nice with 7.6 and 38 or 40 Talons, 42 too in very light stuff; but never really liked it with a 7.0. The '11 66 instead had great control in messy chop and overpowered, but asked for more fin: a 38 Talon was extremely nice with a fully powered 7.0, 40 felt smallish with 7.6 and the Talons generally felt not enough powerful (probably a Vector Volt would be OK on that size and vintage).
I ordered a set of Sonntag SL-P fins for the '11 boards and received those at season end. On the '11 models actually felt very nice, more powerful but easier through chop than the Talon's.
The '12 SL66 was changed and is a fury: same as the 58, it has plenty of lift and terrific accelleration. The flexy, powerful carbon SL-P's were impossible to use on that one once powered up. With 7.0, I started trying with 37 SL-P, went down immediately to 34 and that worked only when just 'nicely' powered; in the end I tested again the Talon 36 and unexpectedly (SL-P's were easier on '11 board!) it was a lot better.
The last session I had on the 66 was in terribly messy waters, crossed waves (it was about 20 + knots onshore Southerly wind a few hours after a 25 knots SW), with 7.0. At first I tried the 36 Talon but didn't even dare to sheet in and use my harness on the (hardest) port tack; then I fitted a 35 Vector carbon Rockit: at last it was perfect, with incredible control and incredible performances. I was astonished at how the board's behaviour changed. I am buying that fin, plus a 37 for the 7.6 and the 31 fr the SL58.
Actually I didn't test the SL78 enough, but I think I will use the 42, 44 and maybe 46 Talons on that one. I also have a (rather soft) 46 carbon Canefire and that one is for super light winds, as it proved way too lifty on former '11 75. I am selling all of my SL-P's (34, 37, 40, 43, 46) as have way too much lift for the '12 boards that I am NOT going to change this time.