I agree with Screamer. The Freeride flow will not add significant upwind drive compared to the Crossover. In fact, unless your in very high speed mode, the extra profile of the Crossover might even prove more effective upwind, particularly in the kind of hard upwind/short distance you're talking about.
Again agreeing with Screamer, I think the Crossover is simply a better fin.
As for size, it is highly personal. Both 30 and 28 would be OK. Also the 28 will give you SIGNIFICANTLY more upwind drive than your current fin and for most persons be OK also with a 6.5. I use the Crossover 28 all the way up to 7.0. BUt other might prefer a bigger fin for different reasons.