I have the Sig Extra as well as a number of other arfs. I use ball links with 4-40 rods on all of my control linkages. I like them because they eliminate all the slop that you'd get using clevises and such. The hardware that comes with most arfs are junk. I also use aluminum servo arms and very stiff horns (currently Sullivan metal horns on my 1/4 scale arfs) on the control surfaces. I've never had one fall off or wear out, and I've never had any flutter either.

I'd recommend you stay with the ball links and good stiff rods. Make sure you're using servos that are rated 70 ounce/inch of torque or better on that plane. (You'll want more torque on the rudder of course)

Have fun...