Upside down decals???

No, don't put it on upside down.  Normally, there is a backing panel that you put the decal on, then the front of the panel is another piece with the instrument bezels on it, that you put on top of the decaled back piece, sandwiching the decal between the two so that the dials show through the holes in the front part.  If you don't have the flat back piece, you can either place the decal on top of the front piece and use decal solvent to hopefully settle the decal into the recesses, or you could just forget about it and paint the panel black, as you usually can't see the decal instruments anyhow after you complete the build.

or

just cut a piece of plastic to form the new back plate (to attach the decal on) cut to fit;

 apply the decal to this  

and put the instrument  face (with the holes) on top of the decal (after painting it.first)

Good luck

Thanks for the info guys....

I think I'll cut a piece of brass or aluminum for a backplate; paint it the proper color, apply the decal, and CA it to the clear IP.

I'm sure the CA will mar the IP some, but I should be able to paint over it.