Thought I'd update this with the back box re-decal job.  I did it dry as for the cab but decided to try something different to finish the edges as the gloss paint pen wasn't going to match the satin paint of the back box edges.

Step one after installing and trimming the decals was to carefully mask the decals to leave the white trimmed edge exposed.

I then  sprayed the edges of the cabinet with a few coats of satin black.  The masking tape was then removed to leave decal edges that were sealed to the edge of the cabinet.