I am building forces in 6mm specifically for O Group, based on 1:1 scale.
British company and some support (please excuse my painting)

For my tanks I decided to use 2 tanks on separate bases for each 15mm model. This allows them to be placed either side by side or one behind the other if going down a road. The 2 bases should always be in contact. It allows the removal of one model if there is a "damaged" result - for quick visual reference.
So this pictures is equivalent to 4 tanks at 15mm scale (again excuse the painting)

Still painting these (very slowly) so no in-game pictures yet I am afraid.