Release of flowitems from source at once

Hello sebastian,i am basically from mechanical back ground,so i do not have good touch with programming,but i can understand what's going on internally.
Regarding my problem I given my batch size and distribution in previous models
I have three items with batch sizes 15,16,17 and having exponential distributions 10,15,20
In my project work i have 74 items.each source having 5 to 10.Totally there are totally 13 sources each having unique distributions.I saw your model just now it is correct when it is created with one source.I have 5 to 10 items in one source so i should dynamically change its batch size content when a new flow item enters into the queue.So i am trying to do logic in the source itself.

Jorg,i am very happy to have different approaches to the problem.I will try to do mixed approaches of you and sebastian.But the method of solution i am seeking will suit my problem.Please advice