The most stable way I have imported Hi-8, VHS, mini-DV etc into a Mac is using a Blackmagic Intensity Shuttle bought on ebay (Thunderbolt or USB3) and using Media Express to do the import. I also have a in a TBC for the VHS import. After import then use FCP7 or X or whatever for editing.. Importing using FW800 into any of the NLEs or iMovie is fraught with problems .. timecode breaks etc.