people here are running many versions of ACAD. The versions running here are ACAD 2004, 2007, LT2004 and LT2007. Is this mix of software wise? Would it be better to just have 2007 across the board? Are there obstacles that could potentially slow production? The habit here is to save files in the default format. I have thought of setting the default on all of installtions to 2004, since 2007 is backward compatible. But there is a user here who says that there are elements she uses in drawings that would not appear in the files if saved in the 2004 format. What kind of 2007 elements would be absent in 2004?