V6 makes massive files if inserted files have textures and the default setting of “Save textures” is on.
In other words: A master file shall NOT store the textures of linked files.
This is easy to duplicate:
1- make a new file and insert an image.
2- save files as XREF-image (or something else ;))
3- make a new file and insert the XREF-image file as LINKED
4- don’t add anything else and save file as MASTER
5- check MASTER file’s file size and see that it rather big.
6- now go back and SaveAs the MASTER file and toggle off “Save textures”
7- check file size and see how small the file now is.