Compressing 720p timeline to standard def DVD

Apologies if this is elemental... I've graduated to HiDef editing only this past year. But I've not yet had to author a standard def DVD with a hi-def timeline (up until now I've been doing direct recording to a Pioneer LX1 recorder via Kona LHe card).

I edited a piece in Final Cut Pro, 720p timeline running at 59.94. No matter what I try, I can't get a nice, standard letterboxed DVD that plays smoothly. Either the DVD picture stutters slightly as it plays (presumably because half the frames were thrown away to get to 29.97), or I get a rapid overall flickering, as if every other field is gone.

My latest attempt: export the 720p 59.94 timeline self-contained. Bring it into After Effects. Drop that into a DV comp sized at 720 x 480. Scale the 720p movie to fit (51%). Render to Photo JPEG, lower field first. Bring that into Compressor (standard DVD, highest quality), then bring those assets into DVD Studio Pro. All is well, the DVD plays, except the DVD has all these anomolies that sure suggest something didn't get de-interlaced and/or transposed to 29.97 correctly.

Anyone know what the magic switch is that I am failing to throw?

Thanks, Larry