in my experience, any SD codec that starts with “DV” is lower field first – all the others are upper field first … fcp will let you think you have change the field dominance (eg, changed uncompressed to lower field first) but when you play it back it is still playing with the appropriate field first for the chosen codec
i learned this the hard way trying to export dvcpro50 edits to an avid system that didn’t support dvcpro50 – i ended up converting to uncompressed and adding a shift fields filter to every shot
if you set fcp to use none (no field dominance) it will play the footage as if it were progressive – this can look a bit jerky if the footage is actually interlaced (although not quite as bad as the wrong field order)
btw, if you copy an fcp edit from a lower field first sequence and paste it into an upper field first sequence it doesn’t automatically adjust the transitions to work upper field first
sorry, i’m getting off-topic so i’ll go now
jjjjjj