This is going to vary from cocker to cocker- that is why they made it adjustable. I use a TPUL of about 10 TREL of about 6. I don't get bounce at all. A teammate has his at about TPUL 20 and TREL 10. This slows things noticeably, but he needs to do it to keep out the bounce. Depends on the weight distribution of your marker, the weight of your internals, mainspring tension, flux capacitor charge, your smiley bar compression, and the openness of any connuter valves.