My idea is to use a z-bend to connect to the servo arm and then a threaded clevis to attach to the aileron torque rod.

IMO, that's the absolute best method of connecting a linkage. You should never need more adjustment than the single threaded clevis provides, and the Z bend makes a connection that has no slip and absolutely won't come apart.

That being said, there's nothing wrong with solder clevises, provided you use a couple of tricks when assembling them. Roughen the rod with sandpaper and use a rotary tool or file to cut crosswise grooves in the rod where the clevis will attach. Use a good rosin core solder and a HOT tool, like a Weller gun. Don't use a soldering iron. Make sure the joint is bright and shiny and DO NOT move it until it's completely cooled.

Dr.1