Wheels for pet carrier

When I bought my pet carrier I didn't notice wheels were important until my first flight with it. I had to lift the box and carry it with my hand, while the other hand was pulling my luggage. 
I instantly ran out of hands.

I created this design where I can slide the wheels in, secure them too (with zip ties or such) if required, and pull the transport box using my dog's spare leash.

The dog is NOT inside the transport box when I pull it.
Wheels are for when I have to carry the box from the parking lot of the airport to the oversized baggage drop. Or from the baggage claim area back to the car upon arrival.

Here's the reason why I choose small wheels, which are obviously not the best, but I can put them in my pockets easy.
My design lets the wheels slide laterally into the printed part(s) and these hold them tight. I didn't even need to secure them, although I created small holes to secure the wheels to the backplate (stl) with small zip ties. But I didn't use them.

Original post:

Link to my Reddit post with short video

What you need:

• 16x 3,5x16 chipboard screws - see photo
• 4x wheels - see photo

Printed with:

• Sunlu Black PETG - Exception for TPU, I believe any material would just do it. 

Print settings:

You can print it however you like it. The only thing to take care is dimensional accuracy. 

I calibrated my printer flow to perfection, meaning that a 40x40 cube with a single wall having a 0.4 line width in the slicer (I use Cura) MUST produce a cube with each wall of 0.4mm - see photo