Hi Rene,
The nice thing about a portfolio of EAs is that when a few of them are going through a drawdown the others are profiting which smooths out the balance line so the overall drawdown is less. One way to determine the overall drawdown is to run the portfolio in a demo account for a month and then determine what the overall drawdown. From that you can then calculate lot size based upon the account risk you are willing to accept. It sounds like you have EA Studio, so you can add the EAs to the portfolio in EA Studio and look at the stats to determine the overall drawdown and then base your risk from that.
It is very unlikely that all 10 EAs will hit SL but how many of the will? So you still have the same issue as to how to determine risk.
Alan,