I decided to have go at printing a test overlay, this is a multi step process and not a professional one.
1) print overlay design onto acetate sheet, using a colour inkjet and transparency sheet
2) Cut acetate sheet down, making sure that the overlay is smaller than an actual real overlay
3) Laminate the acetate sheet, this stiffens it up enough to stand up (could double laminate)
4) hand paint a white mask on the back (took a couple of coats of white primer)
first coat pretty thin everywhere
view from front
5 Tidy up mask edges with scalpel
Before tidying up it looked like this
back after tidy up (it’s not perfect but good enough for testing position of elements)
front after tidy up
Overlay on the Vectrex
Can now start tweaking lengths and positions.