RE: shallow water
Hey mate, I understand the long fin in shallow water problem.
I sail a Free Formula 198 that is 90 cm wide with a 65 cm fin most of the time here in central Ohio in the US. However, on light wind days I sometimes put on a True Ames Shallow Water 38 cm fin that works well for me.
I have used the 38 cm fin with my 10.0 Retro in 10 knots and could still go upwind. I also used it in strong wind witha 5.5 Retro and that worked too.
I just got back from 3 weeks in Bonaire and the water there is really shallow at low tide. I rode the HiFly Madd 165 that comes with two 36 cm fins. However, those are too long for there and I used my own 30 cm True Ames Teardrop fins. They worked well for up to 8.0 sails. I even used 25 cm fins a couple of days with a 5.5 sail. You can get used to shorter fins in a couple of days. You just can't push on the back leg against the fin until you're going pretty good.
The local pros use very short fins and do amazing free style in about calf deep water.
Let me know if you try the 38 shallow water fin. I got mine from Isthmus Sailboards in the US for about $100. I think it might be the answer you're looking for.