AppEngine and big WebGL.data files

Hey, I'm trying to set up a WebGL export to App Engine. Short version: where does Unity call the WebGL.data file, and can the location of it be changed? And especially can it be done for cross domain items

Longer version: My WebGL.data file is 80 mb in size, or 30 when compressed

The issue is that that App Engine doesn't allow file hosting of files larger than 32 mb, so the 80mb file can't be uploaded, and AEG compresses files itself so you can't flag the 30 mb file as "compressed".

What I've done is set up the file on Cloud Storage and fetch it using blobstore.Send whenever the WebGL.data url is called. This works perfectly for the 80mb file.

 func handleWebGLRequest(w http.ResponseWriter, r *http.Request) {
     c := appengine.NewContext(r)
 
     blobKey, err := blobstore.BlobKeyForFile(c, "/gs/<url>/WebGL.data")
     if err != nil {
         fmt.Fprintf(w, "Problem: cannot find WebGL.data")
         return
     }
 
     blobstore.Send(w, blobKey)
 }

However, bandwidth, and worse, loading times for the 80mb files are very long. I'd like to upload the compressed file and have it sent over. this almost works, the file is on cloud storage marked as compressed.. except sending it through code makes the content-encoding header "disappear" and it doesn't look at the file as a compressed one.

Alternatively if one tries to mark the file as public and simply redirect to the url provided by cloud storage, this again almost works, but a cross-domain policy problem pops up

 http.Redirect(w, r, "http://storage.googleapis.com/<url>/WebGL.datagz", http.StatusMovedPermanently)

So my question is, is there a place I can change where the WebGL.data file is called? maybe if I can make it cross-domain-able this issue will finally be resolved. Or any other suggestions