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Building Irregularities

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Greetings all;

I am designing a two story CMU building in seismic zone 3.  The second floor diaphragm is a cast-in-place concrete slab.  The building will house dewatering equipment at a wastewater treatment plant.  For process flow reasons, it is desirable to offset the lower level of a shear wall approximately 4 feet from the upper shear wall (offset perpendicular to plane of wall).  A co-worker has advised me that shearwalls with this type of offset have not performed well in recent earthquakes.  He also said that the 97 UBC also penalizes this type of discontinuity.  The only reference in the UBC that I could find is in section 1630.8.2.1, which references Table 16-L.  To qualify as an irregular structure in Table 16-L, my offset (Type 4) must be greater than the length of my wall.  My wall is over 50 feet long, but the offset is only 4 feet.  Is this really as bad an idea as my co-worker says it is?  Besides deflection compatibility, and drag forces, what problem areas should I look out for?

Kipp Martin, P. E.