It is something you will have to play with. I don't think running 48 concurrent engines would be a good ideal. You have to look at the memory that is used by each task and then save resources for the OS and QVS.
As I now ,distribution service himself is controling quanttity of paralel reloads (by setting in QMC). For example if you start 40 tasks at one time but setting is 9 - at same time will be working only 9 but all 40 tasks will be done.
And these 9 tasks will use significiant resources anyway.