LLG wrote:I've heard the Greeno,... I think it is called.... is excellent,
That's a Greenough as in George Greenough. Good fins for sure.
General rule of thumb is the more surface area on the fin, ie, the wider and taller then the more drive you will get. The downside is you will lose a lot of manouvrability. The narrower the fin and shorter, the looser your board will feel but you lose drive, power and grip.
A good nose-riding fin needs lots of surface area but you still want to be able to turn your board. So choose a fin with a nice wide base, that still has plenty of thickness through the middle then narrows through to a thin tip. That will offer you a nice mix of both characters. The Joel Tudor fin mentioned above is a good example. Go for about 8.5" to 9". Anything more and you;ll not be able to turn your board.
I have a 9.25 Josh Farberow Flex fin in my board. The Greenough 4C would be good for you too.
Feel free to PM me if you want to get more suggestions.