And to answer Dux, IIRC, the number 5 plane does have the number painted upside down. At least on one side of the inlet.
I'll dig through my photo albums and see if I can find a pic of #5 on the ground/flying level.
[Edit: I found
this pic online. You can clearly see the upside down 5]
There are some great pics on that site. Looks like the 5 on the other side is right side up...

Cheers,
Spitter