am in the process of a full explanation of how to add forums with split cats.
there are some conditions that need to be used.
a cat must always be on the top - act as a forum set to "No".
another cat may be used if its the last one - or all cats in a group .
wrote this up - need to do better in the pre sales questions :
Before you buy a Skin, style .. .
should help - still have problems, need a screen shot or link to see it and can get you fixed and continuing on your way.