Thanks, Emil...
The inside's inside the outside. As you can tell from the tape, there's a lot of inside to get inside... Interesting popping and clicking noises as it flexes into place, but I don't think anything critical has fallen off.
One important point: if you do as I did and fix the front bonnet into place to beef up the structure, before you glue it, tape the body shell down on a tile or glass sheet to ensure the base is completely flat. On mine, the "nose" ahead of the front wheel arches droops slightly, which makes it harder to get the front of the undertray in place. I don't know if this is a result of gluing in the bonnet panel, or just another example of the potential for warping this fragile bodyshell in the box.
Now to leave this to set very solid for a good 12 hours.
bestest,
M.