Eugene,
  Here's some input on your questions from my ES:
1.  I put my RMI micro encoder temp probe on the underside of the wing
beside an idler arm inspection panel.  It's flush with the wing skin.  Seems
to work OK there.  I've also seen them put inside of the NACA inlet on the
vertical stab.  Just be sure to keep it away from the exhaust flow so that
doesn't skew the readings.
2.  No, you don't put both latch mechanisms in the door- it's one or the
other.  I used the newer ones rather than the pins.
3.  Here's the link for the airbox:
http://www.topflightservice.com/VentBox.htm .  I highly recommend this type
of installation- it makes a big difference in the volume of air flow when
the door's shut and can help cut off the air from the tail when you don't
want it.
4.  Here's the contact for the inertia reel system- (I believe they may now
be stocked by Lancair).  Contact Tom Hodgdon at Amsafe Aviation in Phoenix,
e-mail: THodgdon@amsafe.com .  He can either get them for you or tell you
where you can get some.  They're a big improvement over the stock belts and
can be ordered in a color of your choice.
  Hope this helps,
  Skip Slater
  N540ES