Generally on EVOs, moving back the fin will not always help with upwind, but since your problem is not technically upwind per se, it might be worth a try.
You might try changing boom height too. Try a bit both lower and higher and see if it makes the board control easier.
BTW, I have a 30cm Drake Freeride flow, never used. If you're interested I can check postage from Sweden to Switzerland and you can have it cheap. A little big maybe, but worth a try in the light of Floyds experience.
I may have a Drake crossover somewhere too, not sure about size though.