Hi Brian,
If I understand your goal correctly, I don’t think you can achieve a gap-free, non-overlapping wall from four cubes of different lengths using a Cloner, because the Cloner only controls spacing along the three axes — it has no awareness of each element’s actual length.
Say the cube lengths range from 100 to 400. If you set the Cloner’s spacing to 100 or less, you’ll inevitably get overlaps, since some cubes are longer than 100. If you set it to 400 or more, you’ll inevitably get gaps, since some cubes are shorter than 400. And if you set the spacing somewhere between 100 and 400, you’ll still end up with both gaps and overlaps, because some cubes are longer than that value and others shorter.
Introducing randomness, or changing the seed, doesn’t help either — it only randomizes which cube gets placed where, not the underlying mismatch between the Cloner’s fixed spacing and each cube’s actual length. So a different approach is needed.
I’ll look at some of the easier alternatives and explain how to do it here. I hope this has been helpful so far.