As told new version 7.0 allows the use of logical interfaces to permit to terminate VPNs on them. I would ask you if static rule is implicitly told to do this. Because PIX, AFAIK, doesn't permit assignement of IP address belonging to the same network range to two or more interface.
P.S. Is already available 7.0 series release for PIX 515? Or do we have to wait again?