I want to add a number to the front numberboard of  life-like Proto 2000 gp-9.   The loco came without any number.  I have created the number that I want (white on black) and made it just about the right size.  I will not know for sure until I attach it.  I had assumed that when I took the shell off I could apply it from behind.  However, there is a solid piece of clear plastic where I would want to apply the numberboard from the inside.  I cannot get it out.

Is there some way to get it out or do you apply the number of the outside (trim it carefully)and cover it with some kind of clear lacquer. Or is there a better option.  See photo of clear plastic piece below.