yeah the reason why it took me so long is because I could never find an 8 player online group all willing to do the challenge for some reason. it would always end up with someone leaving.
When i tried to start my own, no one would join. so eventually I found an 8 player group doing freeburn challenges and i asked the group leader to change the challenge to the baseball stadium. I did that four times – the first three group leaders just ignored me completely.
Goes to show what the ps3 community is like. ~not too friendly.
I'm just glad the fourth guy was willing, cos I was gonna give up after that.