Yeah, avoid rocker arm stoppers at all cost. If you get valve float you would rather throw the rocker than have it stay in place for the piston to come back up and hit the valve. Seen way too many motors destroyed because of rocker arm stoppers. Even without doing the twin grooved shim mod you can still rev your valvetrain to 8k with the s4s and stock springs and retainers. Even more safe with some BC springs and titanium retainers. I would do springs and retainers though. Its insurance and at 8k you wont be floating the valves at all.