Pete,
The right combination is to stop immediately what you are doing. The BVV-5/VA-500 is absolutely the worst quality betacam sp playback option possible. The VA-500 does not have a time base corrector nor any drop out compensation.
The 5/VA500 is simply for playback confirmation in the field never to be used for any quality playback or capture into a NLE. The unit does not play back at unity reference video levels.
Composite playback with the VA/500 will offer you the noisy, lowest resolution playback image possible. In addition it is highly unrecommended to use a field recorder for constant playback as this was never the intended use.
There is absolutely no sense in trying to capture at 10 bit uncompressed given the fact you are throwing away all the image quality right from the beginning.
Do yourself a big favor and rent,borrow or steal a studio betacam vtr such as a pvw-2800 or bvw series which have tbc’s as well as rs-422 control for capturing into FCP.
Use the right equipment for the right job and you and your client’s will be much happier.
Tony Salgado