If you want to stay small use the reactor rear set. These are the most upright and pivoty fins FCS has for the FCS2 system. These are the same fins Ashley Kidd likes to use. They are not designed as a lead fin but they are pretty good, and the 80/20 foils works well for wakesurfing. They are in fact somewhat similar to my standard wakesurf fin.
http://chaossurfco.com/wakesurffins/...-quad-rear-set
If looking for a bigger fin, go with the main Reactors. I find the Neoglass to be the best value. Not a standard molded plastic, but not as expensive as an typical RTM.
http://chaossurfco.com/wakesurffins/...-glass-tri-set
Nick