Before we deal with the inner layer, there is a small piece (it is not present on the template files) we have to add to the back of the dome base; the purpose of this piece is that the red rim's thickness on the back area of the dome is double compared to the rest of the parts. You have to cut a 330mm long and around 10mm wide strip from 2mm thick cardboard, then bevel around 50mm from both ends so that when it is glued to the dome base, the cardboard strip will flush with the rest of the parts: