I point mine up so I don't snag it when taking off the tail dolly!

I thought it best to point it whichever direction will keep it as
perpendicular to the airstream it's reading from for as much of the
flight regime as possible, in an attempt to keep the flow within
+/-20deg to keep the probe from reading erroneously.

Mine points down, and is really short too! I have a cruciform
tail though, so I don't get probe envy since it's well clear of the
bow wake of the tailplane. In fact I prefer it this way and well...
at least my vario tells me size doesn't matter

-Paul