Storage box for low-loader Siku scale 1:32

As a follow-up to the extender for the low-loader, my 9-year-old son has now designed and created a storage box as well. This box fits neatly over the edge of the low-loader and can be used to store all kinds of accessories, such as tie-down straps, wedges, and more. He handled all the measurements himself, showing impressive creativity and problem‑solving skills for his age.
There is always room for improvement, of course, and we would greatly appreciate any feedback you can offer. Every tip helps him grow further in the exciting and ever‑evolving world of 3D design. Thank you in advance for supporting his journey — it means a lot and motivates him to keep learning and building toward a bright future in 3D.