"For the last and final time SATCOM SATCOM SATCOM !!"
It's a hard crowd here, isn't it Max ! :-)
For the disbelievers...
If the 400 Satcom has a dual antennae installation, then this is the most likely place for them. These antennae are fairly thin and would suggest a patch. A single antenna system has a top mounted antenna and can be quite bulky.
Satcom ops manuals suggest that the side mounted antennae should not be used when door 4L/4R are in use.
GPS antennae are about the size of your average computer mouse (only flatter).
Rgds.
Qavion.