I need to add some 1mm high bumper codes to a 1/72-scale Abrams, and only have a limited selection from a spare decal sheet (the markings are different from those provided with the kit). Rather than struggling to align these on the model, I am wondering whether it would be successful placing each letter/digit on a piece of clear decal, sealing with matt varnish, and applying the panel to the model. What concerns me is that the varnish may prevent the clear decal from separating from the backing paper. Of course, I could experiment with the idea, but I only have enough of the correct size, and don't want to waste them. Has anyone tried this method?

Your local hobby shop may have a product which is called liquid decal film. You paint it on your decals and they dry into a layer of new clear film. Then trim as needed and use like any other decals.