I designed this stackable and expandable storage system for my 1/28 scale Mini Z cars.

The shelfs have posts that fit inside of the counterbore of the bottom of the next shelf above.

For the top, I just made a shelf without the posts.

It works for 94,98,102 mm wheel base cars.

I print them in pairs and it takes about 13 hrs for a pair at 20% infill.