I was just talking mechanically, i was not really talking about cosmetic.

You goop the inside not the outside as i am sure you know.

The only way to fix it cosmetically would be a plastic body filler, ( bondo )

but then you will have mismatched texturing after sanding.

I think the goop will hold it together nice and tight though. maybe the crack might not be so noticeable once goop is dry.

maybe something else would be to try is epoxy and maybe a clamp, pressing the crack together as tight as possible.

maybe wipe off the excess before it sets up.