Open the Revit.ini file in Notepad. It can be found here:
C:\Program Files\Revit Architecture 2009\Program\Revit.ini
Add the following line:
The value of “N” has a default of “8” so you need to increase this value. A good point to begin is to double the size. It is best to do a search for this text to see if it has already been changed in the ini file.