Tell us about yourself!
Instead of free-hand paint the white symbols, could you have used the printing program to create an embossed space? Then, just fill in the depressions with paint and sand off any excess above the short "rim". It would be neat, and easy (with the design and printer doing the fine work). But, I do not know the program, so I do not know if it is easy to add specific "negative space".
It looks very sturdy, and I can see your grandkids putting them up in 30 years. But did you really measure so well that you did not have to cut any plexiglass on site?