https://youtu.be/K7iYy-WE5Kg
WE DUN NEED NO STEENKiNG LATERAL STABEELITEES..!
18 inch span, no steenkeeng diheedrals, no steenkeeng expos...!
If the OP's plane in question is too heavy, it will seem too sensitive if it isn't flying fast enough.
The stiffness of the linkages ought to be checked with moderate hand pressure while the radio system is turned on. Check the linkage while idling and when the surfaces are deflected.
The most slop free aileron torque rods I've ever rigged were greased up good with axle grease, then directly embedded in a mixture of balsa dust and epoxy. Of course, the "trenches" that the torque rods lay in need to be large enough to accomodate the puddles of "epoxy dough". Make sure the torque rod "axles" are greased thoroughly..!
The "Moment of Truth" comes after the "epoxy dough" torque rod bearings cure and you check to see that the torque rods move freely.