It works for me also in game, below you find the end of my test description.lua file.
}
name = "- USN VFA-106 Gladiators - (c.2016 AD-301 - NAS Oceana - XO)"
countries = {"USA"}
custom_args = {
[27] = 1.0, -- Tail change of type of board number (0.0 -default USA, 0.1-)
[31] = 1.0, -- Tail First Digit
[32] = 1.0, -- Tail Second Digit
[442] = 1.0, -- Tail Third Digit
[1000] = 1.0, -- Flaps
[1001] = 1.0, -- Nose
[1002] = 1.0, -- Kuwait Squadron
[1003] = 0.0, -- Australian Squadron
[1004] = 1.0, -- Finland Squadron
[1005] = 1.0, -- Switzerland Squadron
[1006] = 1.0, -- Blue Angels Jet Team
[509] = 0.5, --Helmet Change
}