Is that what you meant by "kicking in at either top or bottom field".
Yep, that's what I meant. I just assumed when I started all this that the capture card would decide at its starting to always do the (field) capturing one way, the "best" way -- or that at least I could click a setting somewhere to force it to start the capture only when the requested field passes through its clutches, the way your canopus appears to do (according to your edit text above). As you may know, the PDI Deluxe capture card is well regarded, 'twas used for the X0 project, so I can't imagine this 'problem' I'm having as being a real one. Did the X0 people really have to do multiple captures to get ones that "took" right and disgard the ones that were the wrong field first? Or is there another piece of this puzzle I don't know about? I'm just not finding that friggin' control/option select which I think must be there somewhere!
I know they could probably answer this at doom9.org (where I've read gobs of stuff over the years of course), but I feel I have already have too many memberships on bbs's going, and my signing on here has to do with more than my wanting to ask one technical question about video capturing -- but I'll keep that reason a secret for the moment I think.
If after a while no one has an answer I'll go over there, but I'm not in a huge hurry on this project or anything.