If you don't do any practice lap and manage you trigger finger well you should be able to pull off a 20 min. main with a 6000. However, Imo, a 6000 makes too heavy of a buggy trying to run with the expert nitro guys. Actually, my 8ight needed to go on diet with a 5000mah 20c Enermax. At some point the loss off handling for extra runtime overcomes the ability of setup changes to compensate for it. Here is a link to Mike's Polyquest 4s 6000mah 25c pack.......625 g's!
http://www.rc-monster.com/proddetail...=PQXP4s600020c