i replaced my rear shocks

new shocks in back of 2004 crossfire. the top nut torque was i think 13ft lbs.
not being able to use torque wrench. i think mine, not tite enough. when i
go over speed bumps, dips on highway, it sounds and feels like its
bottoming out.i heard to tighten top nut until top rubber grommet, squishes
down to same diameter as the metal washer. is that good enough? cuz i
think theyre too loose..