Loading uneven load

I will have 6 water tanks on my lorry. 1000L each, half of them full. They will alternate so group 1 (the full) will cycle to empty and group 2 (the empty) will cycle to full. This is for a white and black tank water system.
What is the best layout for the load???
i was thinking this:
full/empty/full

empty/full/empty

is this the best for stability?

What size/weight vehicle are we discussing?
Are we talking of 6 IBCs?