Coat of Arms Grand Quartering

[nmpolo]

I'm working on a mod and adding coat of arms as a part of it. I've found it really easy to quarter the coat of arms. For example, the House of Trastámara:

trastamara = {
    sub = {
        parent = k_castille
        instance = { offset = { 0.0 0.0 } scale = { 0.5 0.5 }  } # top left
        instance = { offset = { 0.5 0.5 } scale = { 0.5 0.5 }  } # bottom right
    }
    sub = {
        parent = k_leon
        instance = { offset = { 0.5 0.0 } scale = { 0.5 0.5 }  } # top right
        instance = { offset = { 0.0 0.5 } scale = { 0.5 0.5 }  } # bottom left
    }
}

house_trastamara_aragon = {
    sub = {
        parent = k_aragon
        instance = { offset = { 0.0 0.0 } scale = { 0.5 1.0 }  } #left
    }
    sub = {
        parent = k_trinacria
        instance = { offset = { 0.5 0.0 } scale = { 0.5 1.0 }  } #right
    }
}

However, how can I do Grand Quartering where there are more than 4 divisions on the shield? I want to add a coat of arms for Spain that quarters the arms of the House of Trastámara with the House of Trastámara-Aragon but when I try the following, it doesn't work at all:

house_trastamara_spain = {
    sub = {
        parent = trastamara
        instance = { offset = { 0.0 0.0 } scale = { 0.5 0.5 }  } # top left
        instance = { offset = { 0.5 0.5 } scale = { 0.5 0.5 }  } # bottom right
    }
    sub = {
        parent = house_trastamara_aragon
        instance = { offset = { 0.5 0.0 } scale = { 0.5 0.5 }  } # top right
        instance = { offset = { 0.0 0.5 } scale = { 0.5 0.5 }  } # bottom left
    }
}

Is there a way to do this easily with inheritance or do I need to manually position each of the quarters using only one level of inheritance?