This is my exact motor distribution.
Also note that the tray doesn’t need to be at full capacity when going up. Rather, it will act like a regular tray bot (deposit 8-9 cubes at once) for some of the match (probably at the start). Then it will be able to use the towers effectively and possibly add to a pre-existing smaller stacks for the later portion of the match.
This would be useful when you’re paired with a weaker team or just a generally more versatile robot for any kind of alliance. If you were to stack on a pre existing stack, you’d only do 4 cubes max at a time, as you said, the mass of the cubes adds up quickly.