layering decals

Second option sounds easier.

Have you considered using the decal as a pattern for a mask? Friskett matt film works well for this. Then you can mask off the area and apply a white undercoat to the decal—or just use the mask and paint the area. If you do that, consider painting the white area silver, first, as that will give better hide and reflectance to the white—cuts down on the number of white coats you have to apply.

interesting, but the decals are quite small numbers and itd be a nightmare trying to mask the shape of them.

 

will try option 2 above and see how it goes.

I tried the same thing, making custom yellow serial numbers for my Doolittle Raid B-25B; found the right font on the web and everything, but no matter what I did, I could not get the yellow "solid" enough to keep it from going translucent. I layered very light gray and then black underneath, allowed that to thoroughly dry and then put the yellow decals on top with just some setting solution, there didn't seem to be a problem with the first layer wrinkling or bunching - but the yellow still faded to almost nothing.

I had to give up and buy aftermarket numbers that were not the correct "steciled" style but by that point I was sick of the whole attempt.

well, just to let you know, I tried option 2 above and it worked great.

The coat of future over the first decal gave a great "grip" for the second decal, and its now pure white with none of the background color coming thru.

Wel pleased with the result.