Gotta develop the right setup to capture 2-cam videos in the Miata. My first 'guess' at that was wrong. Using the long-ish arms on the suction cup mounts results in a rather 'bouncy' video (the forward-looking capture here), along with some rattling as the housings bounced against the glass (I muted the audio for that reason).
'Phase 2' will be captured with the forward-looking cam on the outside of the windshield, and the in-car capture from a GoPro 'Chesty' mount, watching instruments, etc. Stay tuned!