12mm or 1/144. 
If that is a suggestion

for size of figures - not happening ever.

I use (due to legacy reasons- i.e., cost - too cheap

to spend $3 plus for a bunch of figures in mass) 25/28 mm figures for skirmish (Spanish Colonial, Spanish VSF on Venus, Gothic Horror, Old West in "far Northern" Mexico 1830-1845,) and have moved most everything else to 1/600th (If I find I can convert historical into SF then I will sell off my large SF in 1/300th scale/6 mm size.) Terrain compatibility was a key factor in keeping those eras/genres in the larger figures.
The Author's pictures in the three rule books are labeled mostly that scale or 6 mm with a few larger sized figures pictures IIRC.
Gracias,
Glenn