I don’t know if he had to do anything in the background. But check out the formation templates. I was able to do it there. It took a while to figure out speed. I can explain more later
But @stevenlauis the real hero.
Does this actually work? I've tried adding resistance to formation files in DE but I only get errors when selecting the units.
EDIT: I just tested it in AEA and it works as expected. How did you do this?