If there is a bend in a 2-56 rod... and its more than 1 ft long... its probably inadeqate for more than a .46 powered model. The bend invtes rod flexing.

For a real short pushrod... 2 mm (smaller than #2) is OK on a .60 size model's ailerons if the rod is straight. If you have a bend in it... you need 4-40.

See the Goldberg Tiger 60 ARF... It ships with 2 MM pushrods. If you CAREFULLY align stuff to need no bends... and support the long rods at fuselage exit, mid length and near the servo tray... they'll work. Put a bend in the elevator pushrod... and you need to upgrade to CF tube with 4-40 ends. Put a bend in the aileron pushrods (appx 7 inch straight rod) to use a long servo arm a bit of mechanical differential and the outermost hole on the control horn and you need 4-40.

How you set things up makes a difference in how stiff and strong a material you need for the pushrods.