I use the JP Australia Freewave 93 when the winds, but mostly the chop, get too much for my Fanatic Blast 100.

I have the stock freewave fin, 27 CM, what should I use on it for more speed and faster planing?

Sailing on Texas Lakes, but I sailed in Melbourne once!

Gary

Sail sizes?

These are good for those conditions and even the 29 is still surprisingly ok in a lot of wind/chop

Swept pointer, any brand, you'd need 30-32 depending on your weight and venue.
Pure wave, 22cm.

Thanks, I've got a mFC liquid pro 32

If you cannot tell us your sail sizes, then your option is to look at the JP specs ...

example ..
jp-australia.com/p/windsurfing/fins/freestyle-wave-fin/

Sail size AND body weight.