As for the camera mount, I have also tried the manfrotto "magic arm" in conjunction with the manfrotto clamp; in the 737 there are certainly many positions where You can clamp it onto; during T/O and LDG however the vibrations will probably prevent reasonably picture quality.
Once I also had a camcorder mounted behind the (straight) center windshield of the MD80 during cruise. This made wonderful footage.I simply stuffed newspapers above and below the camcorder to make it fit between glareshield panel and overhead panel.
As for the limited space available in the PA34, did You consider a minicamera in the size of 3cm in diameter, which can be strapped to Your headset and tapes the pilot's view? This wouldn't be prone to vibrations
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This Airbus is o.k., but why did it come with a RENAULT key ??