The stats coding is very similar to the first Black Ops,

statwriteddl playerstatslist codpoints statvalue 0
statsetbyname VERSION 0
statsetbyname RANKXP 0
statsetbyname SCORE 0
statsetbyname KILLS 0
statsetbyname DEATHS 0
statsetbyname ASSISTS 0
statsetbyname HEADSHOTS 0
statsetbyname TEAMKILLS 0
statsetbyname SUICIDES 0
statsetbyname TIME_PLAYED_ALLIES 0
statsetbyname TIME_PLAYED_OPFOR 0
statsetbyname TIME_PLAYED_OTHER 0
statsetbyname TIME_PLAYED_TOTAL 0
statsetbyname KDRATIO 0
statsetbyname WINS 0
statsetbyname LOSSES 0
statsetbyname TIES 0
statsetbyname CUR_WIN_STREAK 0
statsetbyname WLRATIO 0
statsetbyname HITS 0
statsetbyname MISSES 0
statsetbyname TOTAL_SHOTS 0
statsetbyname ACCURACY 0
statsetbyname PLEVEL 0
statsetbyname RANK 0
statsetbyname MINXP 0
statsetbyname MAXXP 0
statsetbyname LASTXP 0
statsetbyname SESSIONBANS 0
statsetbyname GAMETYPEBAN 0
statsetbyname TIMEWHENNEXTHOST 0
statsetbyname BADHOSTCOUNT 0
statsetbyname LEADERBOARDFAILURES 0
statsetbyname LASTSTATSBACKUP 0
statsetbyname STATSBACKUPVERSION 0
statsetbyname MAPPACKMASK 0


Just Change The 0 into the number you want and after your finished press enter after the last stat you edited and type updatgamerprofile then under that typer uploadstats-for ex.:
statsetbyname WINS 1337
statsetbyname LOSSES 100

updategamerprofile
uploadstats

im not sure yet how to get these working online still trying to figure it out Im pretty sure you will write them into a EBOOT but idk if u make a save out of it or just go off the EBOOT itself #we will figure it out.....Hopefully soon :/
if you do figure it out plzz let me know k, thnx
#always 15 spaces in between statsetbyname (xxxx) 15spaceshere 1337

Credits:
.Choco- CFG Dump File

They go in the t6mp_ps3f.self.

The string "exec default_mp.cfg" gets executed by the game, what you have to do is relocate where that string gets loaded from and then add your commands after it :p