I have dedicated plastic frame for SJ8 and it is useless when attached to vehicle. It is not rigid enough and it is vibrating a lot.
Click image for larger version  Name:	SJCAM-SJ8-Frame-Holder-Mount-Plastic-Frame-Case-for-SJ-cam-SJ8-Air-SJ8-Plus-SJ8_fdd821f9-1bcd-457c-941d-e8f30b1b59fd_110x110@2x.jpg?v=1559892645.jpg Views:	0 Size:	2.6 KB ID:	17617
The other type of plastic frame comes from GoPro Hero and I use it with Firefly 8. Look at the way of mounting. It is cut between mounting holes and when screwed it is properly stretched resulting in good rigidity.
Click image for larger version  Name:	RAMKA-OBUDOWA-FRAME-MOUNT-GoPro-HERO-3-4.jpg Views:	0 Size:	22.2 KB ID:	17619

Do you know if some other camera has similar dimensions and it is possible to find plastic frame of such type?