GIMP :: Create Subpixel Rendering Of Monochrome Clipart

I want to use a monochrome image to create a (1/3 size) image with subpixel precision. For starters, a pure black&White clipart seems the easiest to do this with. But after toying around some I couldn't find or think of a proper way to do this.

Any method to convert greyscale-antialiased images to 1/3 sized subpixel antialiased ones?

- Scaled the vertical resolution to 1/3
- Created 3 copies offset by 0, 1 and 2 pixels respectively for use in the next step
- Masked out 2 in every 3 colums of pixels leaving R, G and B striped versions.
- Scaled striped component images to 1/3 horizontal resolution
(no interpolation, aligned so that it uses exacly the desired 1 in 3 colored pixels)
- Got stuck with three seperate R, G and B colored component images...
- Posted this question

Also, attached is an intermediate result of my efforts: the combination of the three striped R, G and B versions. Simply scaling the attached image unfortunately does not yield the desired (and expected) result.