ᐅ Fitting Shelves into an Ikea Kallax Unit

Hello
I want to use a Kallax

KALLAX
Shelf unit, black-brown

laid horizontally on the floor as a shoe storage shelf. The shoes should be placed inside the compartments.
To do this, I want to install a shelf board in the center of each of the 4 openings, so I can store shoes both above and below in each compartment.
Unfortunately, IKEA does not offer shelves specifically made for the Kallax.
I found some shelf boards in the kitchen section that I could cut to size and install inside the Kallax:

Utrusta
Shelf board, black wood effect

Would this be the same black-brown color tone, or does anyone have a better idea (shelf boards from other IKEA products) that would be more suitable?
Best regards
Sektionschef

Hello, the bigger issue is that shelf supports do not hold in the thin hardboard panels of the KALLAX walls. That’s why drawer inserts and similar items are always designed as fully pull-out boxes.

Thanks for the tip, IKEA expert!
I was thinking of nailing these brackets on:

And if they don’t hold, I’ll drill through the side panel and insert a steel pin, since I need a shelf in every compartment anyway.
Do you think that could work?
Best regards,
Sektionschef

You can skip the nail fasteners altogether. Using dowel pins will work, but you’ll need to test whether the holes wear out over time. Drilling all the way through on the outside isn’t very attractive if the sides are visible, and you’ll need pins that won’t slip into the wall.

You can skip the nail fasteners right away. Through-pins will work, but you’ll need to test whether the holes will eventually become loose over time.
Drilling through the outer sides doesn’t look good if those sides are visible, and you need pins that won’t slip into the wall.

Thanks! Do you mean those pins with a ring-shaped enlargement in the middle?
IKEA expert, do you know how the outer walls of the Kallax are constructed?
They look about 4cm (1.5 inches) thick but are probably just two thin plywood panels with paper honeycomb in between, right?
One of the outer walls would be visible on my unit. I could screw a wood screw into the outer wall from the inside so that it goes through the inner panel and a bit into the outer panel, but doesn’t go all the way through.
Best regards
Sektionschef

As the IKEA expert mentioned above, this is hardboard (not plywood) – the material also used for back panels. The whole assembly is then mounted on a frame made of particleboard strips and cardboard honeycomb.
Regards,
IKEA-Freund