“Will I lose any quality by exporting/importing from the timeline?”
none at all if you do it this way:
export as a QuickTime Movie,
use the Current Settings.
(also no motion effects or filters on the clips: otherwise re-compression is involved)
changing the sequence timecode is pretty irrelevant, as it will only ever match one of your 3 clips.
now this has certain problems:
like if you want to go back to tape, you cant.
you can hedge yr bets by either:
A- making a backup of the file you create
B- saveing your sync-sequnce so you can re-capture & re-export if necessary,
C- both A+B
the other approach is to sync your multiclip by AUX TIMECODE.
for this you would simply add an Aux TC to the V1 clip,
then go to each of the V2 clips, (the start of the clip say, but it doesnt really matter)
and copy the V1 Aux TC at that point, and add it to the V2 clips Aux TC.
(if all V21 clips are from the one master clip, or refer to the one FILE, this wont work, of course)
however my experience with multiclips (FCP 5.02) is that Syncing by in-point is more stable than syncing by aux TC
and my guess is if you;ve captured HDV as ProRes, you wont be going back unless there’s some unmentionable disaster.
hope that helps,
nick