Sorry Ken. That WON'T work. Hi8 is analog, so a S-video + L/R audio capture device (these are still being sold) is needed. These connect to the lappie using USB2.
The real isssue is Digital8 and miniDV camcorders, which don't support the data protocols of USB - that's why a straight plug shape adaptor won't work.
AIUI, Later devices, such as HDV camcorder while using a DV/Firewire connection apparently do recognise a USB port and adopt the correction transmission protocol - BICBW.