This FAA Order explains how flight tests are normally arranged.
http://www.faa.gov/documentLibrary/m...D/8130.29A.pdf
Something needing a flight test requires the aircraft to be in Experimental category (as, until the test is successfully completed and assessed then compliance with airworthiness regs has not been shown or found). It must be flown by an approved pilot to a plan approved by CASA.
Yes, I agree, there are certainly issues with external fitment of GoPro cameras etc but this draft AC contributes diddly squat.
An Operational Flight Check is a lesser activity to check function for example. So, for a camera, CASA doesn't care if the camera works or not, just that the installation is safe and complies with the applicable regs.
My mini camera is smaller than my thumb. Easy enough for an approved person to assess a safe place for it to go and determine a safe installation. Less significant than a small antenna.
You don't need an exemption for your STC as it is approved but worth reading the relevant STC with the note on checking applicability wrt other STCs fitted.
PS: aircraft should always be rigged within TC tolerances. Flight tests may want it rigged specifically at one extreme of the tolerances.