In my '81 air-cooled I have had a temperature probe wire-tied to the
horn.  That seemed to give a good reading.  If the pavement is
really hot, it reflects that, too.  But being underneath, it
isn't affected when the sheet metal of the bus starts cooking.

When I bought my syncro, I immediately put one in--only to discover
that the heat from the radiator made it useless.  Since it is a
$16 thermo with about a 10' wire to the sensor, I moved it up and
wire-tied it behind the RF headlight.  It reads fine when drivings.
When parked, the radiator heat dissipating biases it some, but after
driving off, it comes back to its senses pretty quickly.

A sensor in the air-intake columns would suffer the same bias
from the hot engine when parked.

I like the Mercedes bumper idea and when I have to replace my thermo,
since they seem to only last 3-4 years, I will investigate that.

                                Richard A Jones
                                Boulder, Colorado