evo 86lt fin set up

hi guys my name is Coskan,

i've bought a 86LT Evo 2011 and it has single us box fin on it but i wanna use twinser fins,i checked on internet yesterday and there are couple of choises but i have no experience before about twinser fins,so if you use this board before pls would you give me some advice? (which brand fin and how big size) im 72KG heavy and im thinking 16cm US slot box twinser but your advices are very importand for me
thank you very much
Coskan