Ready to fit...

Finished and sprayed, these hemispheres are ready to be fitted through the holes in the skirt section.
Glue from a hot-glue gun is a good method of fixing these in place. They will stand a few knocks but will still 'pop' out, should you wish to swap to a different colour or need to repaint the skirt.

For a more permanent and much tougher fit, use fibreglass to hold them in position.
Fibreglass holds them so well that they will not pop out, no matter how much punishment they get!