dave,
good to see you on the forum again. as soon as you exceed the 100°C (212F) at least for a little while you are okay.
Mercedes Benz and Porsche used to let their cars cruise at 82°C (180F) all day and are fine. 180F is the opening point of the thermostat for the
oil cooler.
My 964 sees more 110°C (230F) during racing and 90°C at normal (autobahn) driving.
4 cm (1 5/8") above the pan seems quite high to me. Depending on the
oil which is circulating at high revs - more in the heads, less in the pan.
you may get a false reading at high revs.
I am not sure though (80%?).
dominik