I have a four * 40 that I converted from single aileron to dual ailerons (built up the compartment at almost the aileron center line on both sides) and have been flying it that way for almost a year now. Great control and no slop and provides Flaps (as though they are needed on the Four *). I used the single bend at the servo with one of those nylon clip gizmo's from Dubro and a Dubro heavy duty clevis (2-56).

I have never used solder but that does not qualify that as an answer... I just never used them, but I imagine that they would hold pretty good. The only thing is you have adjustment somewhere and the threaded clevis seems to be the logical point.