Surfing Waves

I lost the center fin on my shortboard somehow (still don't know when and how it happened).. so in the market for a replacement now.

my side fins are FCS G3, with dimension roughly as below:
Base Length = 4 1/4 “
Depth = 4 1/4 “
Rake = 65

So what size center fin should i get? Also wondering any advantage going bigger or smaller on the center fin?

Hi Travel ,part of the functioning of thrusters was based on three equal sized fins sharing the turning qualities, so I'd replace the missing one as without the dimensions of your board you can change the performance dramatically and not necessarily for the better. Better to try different sets
If you have a centre fin box as opposed to the FCS plugs then there could be allowance for adjusting the position of the centre fin and this would allow you to play with different sizes. It is an interesting interplay between rail, tail width and fin sizes and you might want to buy several sets of different templates to try.
If you can, some surf shops have different templates to try, can be a great learning experience, if you surf with mates try swapping amongst yourselves.
Take some time experimenting you are likely to find out much more about your surfing that way.

So what size center fin should i get? Also wondering any advantage going bigger or smaller on the center fin?

Bigger fins stiffen up the board and give you more hold in and drive, while smaller fins give you less hold in and drive, but loosen your board up more. I have found that to small of fins, in good waves you can lose control of your board and slide out. If your fins are to big, your board will be stiff and your turns will be wider and more drawn out. I try to go as small as possible withourt sacrificing the hold in and drive that I still need. Good advice above from jaffa1949 to try ourt different fins, and see what works for you. I like the smaller Al Merrick GAM Fins on my standard all around shortboard.

thanks for both.. i finally went to a local surf shop and got a replacement.. G3 is no longer in production, so i used M3 instead. same size.. the guy from the shop initially suggest to go smaller since our local break is mostly small waves right now, but when he saw my board (6'9 shortie) he changed mind and said M3 is the the right size.. anyway, the board feels normaly again.. cheers