The running clearences on residential elevators differ by type and manufacturer. Check the shop drawing for the unit your installing and make sure it is within the range required by any local code. In general though, less is more in terms of how wide the gap is and I would say that 1 1/2 in would be problematic for a number of reasons. As an installation tip, you probably want to make sure that the shaft size is large enough to leave some room for installation variables and then adjust the final gap at each floor level by installing a custom (level) threshold sill that gives you the exact clearence you want at each floor.
Adaptive Design Mgr.
Aardvark Adaptive Modifications