I've had this project on the back burner for quite awhile now, and I'm just now getting a chance to revisit it. Before making the modifications that I described in my last post, back in 2018 I made a back-up copy of the full .sh3d file (~200M) before creating a new file in which I deleted _many_ objects (to reduce the file size down to ~6M). After upgrading to SH3D v. 6.5.5, I have no issues opening the ~6M file that I created back in 2018, but I can no longer open the original "full" file--or its back-up copy (also created in 2018), and the error message is: Can't open home "/Users/myusername/Desktop/LRHall.sh3d". To no avail, I've already tried your suggestion on the http://www.sweethome3d.com/support/foru ... 6105#26476 page, and I've also researched the forums for similar issues. I appreciate any suggestions that you may have, and thank you again for your assistance.