Adding airstairs to PDMG 737 600

Hi,Like many of you I love to fly 737 and my favorite, by far, is the PMDG model.I would like to add airstairs to the 737600, same way as for the 700, even if I know that in real life the 600 are not equipped, and that PMDG does not offer it as well. Does someone know how to add airstairs to PMDG 737600 using those available in the 700 ?I have found an airstairs bmp.file in the 700's texture folder, as well as airstair information in the 700's model.cdg file, but this one seem to be a coded file (or may be did not open with the right programme) and does not to allow modification.Has someone tried it with sucess ?Thanks for you help,Patrick Jorand, Geneva, Switzerland