To place a
gab
banner
in a postbit, there is an additional step you need to take: You need to create a hook to put $GAB_ads in the scope of the postbit constructor as it is created in a function.
Create a new hook called whatever in postbit_display_start with the following code:
global $GAB_ads;
Then $GAB_ads[x] will show in your postbits
HTHs!