In article .com,
wrote:
...if I recall correctly -- it's been a while -- the hypothetical
"vulcanoids" within Mercury's orbit would be leftovers from the early days
of the solar system...

How stable would be the orbits of "vulcanoids"? They're packed in close
to several planets and the sun.

The Sun overwhelmingly dominates the situation. Perturbations from the
planets generally cause only small cyclic changes in orbital elements,
unless you happen to be in resonance with a planet. My recollection is
that a first look at the stability of vulcanoid orbits concluded that they
were reasonably stable over billions of years.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |