For a bunch of little models that would often times topple over after being moved, I needed to add a little weight to their base. I decided to grab the heaviest washers I could find in my toolbox which ended up being M8 sized (see reference pic above) and model something around that. I measured the hex to be the same size as standard battletech hexes and made a base for land as well as air units.
The washer fits very snug, I never even bothered to glue them in.

----Edit---
I noticed I put the wrong dimension of washer in the description. It's actually an M8
Updated the picture as well

Creality

Ender 3

Doesn't Matter

Yes

280

20

You can print the land unit hex without supports, It's best to print the air unit stand with supports, just to be sure stringing doesn't affect the washer going in.