DNB,
It's safe to go either way! Mine has been going for two years with lower aileron servos only and has been really quite tight. Here's how: Start with a pair of pretty good servos in the lower wing. (I'm using JR 8231 digitals.) Measure the distance between the mounted horns on the trailing edge of the aileron with the surfaces resting centered. The overall length of each rod assembly will be this measured length. Take two 4-40 quick link threaded rods and discard the quick links. Lay one rod facing one way and the other rod facing the other way. (this makes threads on either end) Sweat solder the entire length so that both rods are now a single unit. Take 1/4" K&S airfoil tubing and push the sweat soldered rod unit into the airfoil tubing so that approximately 1/2 to 3/4" of threads stick out on either end of the rod unit. (It will take pliers to force the rod into the tubing for a great friction fit.) Place a small washer followed by a 4-40 nut with some Locktite on it on both ends. Install ball bearing 4-40 ends on both ends of this rod unit. Install the finished rod unit to the supplied horns placed at the trailing edge of the ailerons with 4-40 cap screws and 4-40 locknuts. (A jamnut can go against the locknuts for added safety.) No slop. No flutter. I am using a Zenoah G-45 with a Zinger 18- 8/14 prop and this thing is ballistic with no flutter or slop. The quad servo set-up is fine also but I never take the plane apart so this works for me. (Don't forget to do the top wing mod and make sure you have the new improved mounting brackets installed on the top center of the wing. The old style crack at the 90 degree bends and you can lose your top wing!) Good luck and happy flying.
Terry