Hi again Leonidas,
This info explains just about everything relevant for this problem.
So if you produce 45 kgs of HALB, do you always pack it 8 by 8 and the rest in last case, or there are cases when you pack more than 8 kgs in a case, e.g. 9 kgs?
If 8 kgs is the maximum package qty, then you can use the first proposal I have made, to round up the TR qty in a user exit.
Later, when you pick, if you pick less than 8 kgs that would be fine, but it is important that you have a cap, an upper limit for the qty.
When you pick you will be allowed to pick SU with 5 kgs as well as the full ones with 8 kgs.
So basically you will use standard process, you can use 2 step picking afterwards normally.
First round-up qty's to 8 kgs for every TR.
Group them.
Create TO (batch determination takes place, then storage type and bin determination take place).
Confirm first step (by standard to storage type 200).
Create TO for 2nd step.
Confirm TO for second step (allocate SUs to your TRs).
That should be it.
So I do think that the best place for the development is a user exit during TR creation.
It would be very, and I mean very easy to do that, just a few lines of code.
First query your rounding UoM (get you back 8 Kgs).
Second, just divide your TR qty by 8, you will e.g. get 1,56 and round down 1,56 to 1 and add 1 => you will get 2.
Then multiply 2 by 8 => 16 kgs.
Update your TR qty to 16kgs.
Or you can use any other way of rounding up as you or your ABAP-er finds it appropriate, but in several lines of code you can make this work in the right user exit.
This will definitely cover your process requirement. There will be a possibility for underdelivery, but you need to have that, you cannot get the process 100% fixed as you have a few variables in the process.