After solving "The Riddle of the Round Walls and the Climbing Spiral", I was (once again) trying to make a helical staircase.
After saving my design, which still included help parts and such, I checked the file size and found that is was about 600 Kb. I then deleted all the stuff I didn't need, and only kept the model you can see in the image above. To my surprise the file size still was 470 Kb.
This means that a 130 Kb basic design, somehow swells to 470 Kb just becasue of applying CopyAsNewFurniture and Export to OBJ format. I attach the file, so you can check my design and data.
Hans
helical staircase.sh3d