Richard - wrong answer, but a good try.
Completely different method, but if I told you, I'd have to.........blahblah
The caravan size was dictated by the wheel diametre - the largest that would pass though the neck, as the wheels definitely had to go through in one piece. (in fact they were made from thinned down plumbing olives, 15 and 22mm) The rest of the thing went in piece by piece, joined together inside.
Many observers accuse me of cutting off the end of the bottle, or even - get this - blowing the bottle round the ship/caravan!!
