Revit :: Draw A Railing Using Railing Command?

We're trying to draw a railing using the Revit railing command.  The issue that's coming up is that we want the balusters to be placed outwards from the center (as in there's a post in the middle of the span) and the remainders at the end posts are whatever they end up being.  One of the runs is small enough that the 5' baluster spacing is centered at the space (as if Revit insists on having at least a 5' space in there and it looks like this: |  |       |  | ).  What we've done for now is to tell it to space the balusters exactly the distance from center point to each end (like this: |     |     | ), but that means we'll have to make a new railing family for each run and that's very inefficient.  Is there any way to specify what we mean by center justification?