Printing white "backing" decals (for multi-part insignias etc)

[Evil Eye]

I have a laser printer; not a super fancy one, but a pretty decent one nonetheless, and I have experimented with printing decals. I've actually had a fair bit of luck with them, but there is one issue that has plagued me and everyone else who has tried making decals (at least, who doesn't own one of those £1000+ printers that can load black AND white toner at the same time). Notably, you can't print white, and some colours (notably yellow) are very transparent over dark colours.

 

Now this isn't insurmountable. I do own a white toner cartridge, however it has to be swapped with the black cartridge and prints black as white, rather than enabling "proper" white printing. For something like white squad markings this is very simple; just print black markings on clear paper with the white toner cartridge in and boom! However, if you wanted, say, a white Imperial Fists roundel with the details in black (or an eye decal for non-40K figure kits as another example), this can't be done in one print. And whilst feasibly possible to print the white parts first, then swap cartridges and run the decal paper through the machine again (I've found decal paper taped to a regular sheet both saves decal paper and also allows you to "test" the size and location of printing on regular paper before comitting) the chances of the decal "layers" being printed perfectly without some nasty misalignment is low, as even the slightest error at our scale could render the decal worthless.

 

There is another solution, however; printing the decal as two separate parts, one being layered on top of the other. This is definitely doable, as combining decals in this manner is quite common. However, the problem is how to print the white (or pale) portion. There are two approaches one could take. The first just uses clear paper and is to print the dark parts first, switch cartridge to white and then print the white elements. This would be more time consuming, and in the cases of off-whites would require some guesswork to get the colour right (as you'd have to draw them in "off-black" in the file due to no native support for white outside of specialist software) but would make cutting and layering the decals MUCH easier, as both would be on transparent film. The other approach uses white decal paper as well as clear; white/pale elements could be printed on the white sheet and then cut to shape after the fact. This would be far quicker as you can affix the separate pieces of decal sheet to one "carrier" sheet, and also you wouldn't have to worry about inverting colours, but it does have the downside that the white sheet has to be cut VERY precisely; using the Imperial Fist roundel example, cut too close and the circle will be uneven, cut too far and there'll be white "outside the lines".

 

What do you guys think? I'm thinking that the cartridge-swap idea might be better (it'd certainly make use of the expensive white toner cartridge I bought!) but any advice would be appreciated. Thanks!