I finally made it back to this project and found a solution. Here are the arguments to ffmpeg I ended up using:

• -c:v libx264
• -level:v 4.1
• -tune animation
• -profile:v high
• -crf 16
• -pix_fmt yuv420p
• -x264opts bluray-compat=1
• -vf "pad=width=1920:height=1080:x=-1:y=-1:color=black, fps=ntsc_film"
• -c:a copy
• -c:s copy

I believe -x264opts bluray-compat=1 was the key.