If an object is only xrefed to complete the project and is not part of the final set of plans does it really matter if it is attached or simply overlayed. For example, I must xref a first floor plan, second floor plan third .... etc on each set of following floors in a multiple story building. The reason for this is to ensure such things as mechanical chases, direct supporting columns, and plumbing lines up adequately so as to facilitate construction in the field. The final set of plans will have absolutely no bearing on whether I overlay or xref as I frequently will have three to four floors stacked one on top of another simply to allow me to properly address these concerns. In the end, the xrefs are removed, detatched, unloaded, purged and all is well.....or am I missing the point ....