position field problems in table that's a child in two associations

I have a table that's both a child in an Acts As List association and also it Acts As A Tree. Problem is I want to keep track of their position in the list and rails by default keeps track of their position in the tree (it seems). Is there some incantation that will allow me to do this? I'm thinking maybe I need to override the name of the position field or something but I'm not even sure how to do that? Thanks if you can offer any advise on this. -Michael