What is the best Pull Pull system and setup (line, servo, clevises, control horns, etc.) to use on rudder on a 120 size plane (let's say about 12-14 lbs.) ? Thanks

Check the Don's Hobby they come in different sizes small, med ,large. etc.

epc.

It is just as important to make sure that the servo is enough to do the job but for the cables ss fishing line or dubro cable is what I use and I try to keep the linkages to a minimum(simple) I like to pull test knots by hooking them to a horn attached to a rafter in the celling and standing on a bathroom scale to see how much weight I can lift off pulling on the cable 2Xthe weight of the airplane or to the test of the line is easy too achieve. and it show es you that the not will not pull out If I think of it when I get home I will take a pic of how to tie the knot

Check out Nelson Hobbies,Don's also has a nice set up.

I use Kevlar like this setup:
http://www.geocities.com/roger_forgues/test.html

I should think that the 4-40 Pull-Pull system from Dubro would work great. I am using the 2-56 system on my H9 cap 232 .40 sized.. with a Futaba S9301 (69oz). The plane will be powered by a OS .61 FX....should scream.