I always felt that if you travelled far enough you would move into
the realm of myth, "Falling off the edge of the world" sort of thing.
Hence the increasingly bizarre lands at the margins of the world.
Quite how this would relate to Mr Stafford's (sorry, I'm English, I
can't call him Greg until we've been formally introduced and
said "Good morning" to each other on the train for 7.5 years)
structure of the HeroPlane, GodPlane etc I'm not sure, but there's a
great precedent in Literature and mythology for travelling into the
unkown and it becoming increasingly "mythical". I don't think this is
your state of mind though, this is the increasing oddity of the
unknown as in Excalibur etc.
Mind you, meeting the Crimson Bat could give you a whole
new "internal" perspective on things! Do bats burp?
Mitch