Nest step - coat the panel with clear acrylic paint -

Reassemble the internals -

It worked well. It wasn't perfect but it's my first (rushed) attempt intended simply as a proof of concept so I am happy that this is a workable thing.

Conclusion (thermal):

This didn't quite work out as I expected. I assume the original panel was aluminium (aluminum) painted black when in fact it was plastic coated with black plastic. I then painted the surface white for contrast. This may have helped the adhesion of the toner to the surface so I will do another test with bare metal in another log or perhaps painted metal. It seems to have stuck to the white paint well so perhaps this was an acceptable test.

I will also be creating another log with chemical transfer to plastic.