found another issue. In the threadbit display, when I tell it to display ads after say forums 5|10|15 ..
after 5 will be 1 ad display, after 10 will be 2 ads displayed, after 15 will be 3 ads displayed.
This is both on my "live" board, and test board.
I've temporarily worked around my postbit issues by using custom ads... but that still puts them outside of the postbit area