Hi Burr, yup that's right.

Yannada - that's how you can get your 3 to 7mm offset working currently.

Select your chair, then run Transform/Scale, type 0 <enter> 0.01 <enter> to scale it around the origin to 1/100 of its current size.

Now you can use surface offset in the range that you want, which are now values of 0.03 to 0.07 . I tried several values in this range, like 0.03, 0.04, 0.05, 0.06, and 0.07 and they all work. (above 0.08 or so seems to start to be problematic).

When you are done, you can select the chair and its offset and scale back up if you want.

That will produce the result you are looking for right now.

It may not be too hard for me to adjust the tolerance to be a relative tolerance which may improve things to work better at your original scale, but you can get this done with the above procedure right now.

- Michael