I’m able to stitch it pretty well if I cut it into two images prior to importing into Hugin. That’s not ideal, so I’m still trying to get the single image cropping working right in Hugin.
Once that’s figured out it looks like there are now some tools available to convert a Hugin pto file to a ffmpeg remap filter. https://github.com/evertvorster/dualfisheye2equirectangular_ffmpeg_remap
This would further simplify the process as a directory of images could be remapped directly into equirectangular video with a single pass of ffmpeg.