I will still like to look at the spring set up for the filter cage. The spring manufacturing chap i know. No longer wants to do it. Regarding the Go Pro thumb screws ,i screwed on a m5 nut to take up the longer thread. That worked well. However i have now found some m5x30 long grub screws . I fitted those, then turned some long nuts to fit . Now the foam and outer housing just locates onto the studs. A bit easier to install. IMO