A variable vane actuation assembly for gas turbine engines having rotatable stator vanes comprises an engine casing, a unison ring, a bumper ring, a radial spline connection and a plurality of bumper shims. The engine casing is configured to encase the rotatable stator vanes. The unison ring is disposed concentrically with the engine casing. The bumper ring is disposed concentrically between the engine casing and the unison ring. The radial spline connection extends from the engine casing and joins with the bumper ring to permit the bumper ring to float radially with respect to the engine casing, but prevent the bumper ring from rotating circumferentially with respect to the engine-casing. The plurality of bumper shims are positioned between the unison ring and the bumper ring to limit deformation of the unison ring.