Compressor encoding for DGFastchannel

I've been using Compressor to make material for DGFastchannel with a setup based on their specs:

File Extension: mpeg
Estimated file size: 6.75 GB/hour of source
Type: MPEG-2 program stream
Video Encoder
Format: M2V
Width: 720
Height: 480
Pixel aspect ratio: NTSC CCIR 601/DV
Crop: None
Padding: None
Frame rate: 29.97
Frame Controls: Automatically selected: Off
Start timecode from source
Aspect ratio: 4:3
Field dominance: Bottom first
Average data rate: 15 (Mbps)
2 Pass VBR enabled
Maximum data rate: 18 (Mbps)
High quality
Best motion estimation
Closed GOP Size: 15, Structure: IBBP
DVD Studio Pro meta-data enabled
Audio Encoder
Format: MPEG
Sample Rate: 48.000kHz
Channels: 2
Bits Per Sample: 16

This has worked just fine so far, but now I'm hearing that what hey really want is a 720x512 file. Using "padding" does not seem to make a difference, either. The final result is still 720x480 (according to MPGStreamclip). I could shell out a grand for Episode Pro, including all sorts of capabilities we already have with other aps, but I want to find a way to make Compressor work. Any ideas?