responsiveimages set multiplier based on (backendlayout) colpos and contentelement

[V35CH]

How can I set the responsiveimages multiplier based on the colpos for a specific contentelement (carousel.text_and_image)?

I have tried this:
In the default backendlayout the colpos 8 should be modified.

lib.contentElement.settings.responsiveimages.backendlayout {
    default{
        8 {
            contentelements {
                carousel {
                    text_and_image {
                        multiplier {
                            default = 10
                        }
                    }
                }
            }
        }
    }
}

this works, but effects all carousel items:

lib.contentElement.settings.responsiveimages.contentelements {
    carousel {
        text_and_image {
            multiplier {
                default = 10
            }
        }
    }
}