Stitching help needed

[Anonymous]

I am having some trouble with getting surfaces to stitch together in this particular model. I have stitched many surfaces together already in this model, so it isn't a question of how to stitch, but rather why won't these particular surfaces refuse to stitch?

I have tried every trick I know, from breaking it down to many smaller chunks, building individual faces on their own separate planes, and splitting each surface a little bit back from the join, and making a bridge surface between them.

The validate surface option is not available for some reason.

Any thoughts? 

I tried attached the file to this post but it is too big, so here is a dropbox link to the file:

https://www.dropbox.com/s/aqwbmjttviviuz4/celtic%20second%20dragon%20v13.f3d?dl=0

Thanks in advance.

[Anonymous]

Here is a direct link to the file: http://a360.co/2hGkXi3

[TheCADWhisperer]

Just out of curiosity - can you get anywhere with this file as reference?  (check the surface normals)

[Anonymous]

Flipping the normals doesn't really help because fusion flips the normals when it stitches the surfaces together. I sometimes leave a couple flipped so I can see where I am working visually.