I've heard good things about this McGaughy's kit for the front on the NNBS's (which I assume it will work on the 15's) but it does the same thing as what Tony's talking about without modding the struts (which seems risky to me, no offense to Tony, I'm sure he knows what he's doing but there are others that may not be as careful when doing it).
http://www.mcgaughys-suspension.com...-1-2-drop-strut-spacers-mcgaughys-part-34061/
http://www.mcgaughys-suspension.com...-1-2-drop-strut-spacers-mcgaughys-part-34061/