Onto Mirror plexi, in reverse, on the silver side. Etching the "outside" surface doesn't reflect the LEDs nearly as well, so I knew I needed to etch the inside.
This is all driven by the fact that I only have 3/8" depth under the letters to the top of the PSU and DVD drive to build my lightbox, hence the previous construction with the mirror 1/8" and the LEDs.
Why I didn't think of this before, I have no idea.
So...
I took my existing lettering, my fat sharpie, and turned it inside out:
That left me with:
then I took my dremel with a very tiny tip:
And very carefully, traced the outside most edge of my sharpie path to outline the lettering:
To get this:
Still has the full protective film on the pretty side, I just etch the silver layer off the back side.
Mostly lit up by dropping into my previous lightbox:
a little closer:
And placed behind my metal lettering to show the outline effect:
I will move the LEDs, cover the edges, and then stick it to the inside of the metal lettering for the final result.
I might fill in the etch to make the lettering more solid, or frost some of the front to make the lighting more even. Not sure yet.