DIY Transcoding -- How to upload thumbnails

This was part of an old thread I started in the Shotgrid forum but it seem better suited here.
Anyway I’m trying to do all of our transcoding without using the SG transcoder.

I can get this to work for movie files and images that are uploaded but not for thumbnails.

So for instance, if I have the proper dimensions for a thumbnail , I try to upload to the field names “image” or “thumb_image”.

When I look back at the version, it thinks there’s a thumbnail there but it never shows up. I can even click “view image” and it comes up (saved to the s3 url) but I still can’t see it.

Is there some other step to make the thumbnail viewable on the version?

image

I haven’t tried this with a filmstrip yet but I imagine the result will be the same.

Any thoughts?