Thank you. This was helpful and partly worked. But I had two problems with it. (As a preliminary matter, when converting to cubic curves I got a message about discarding true type information; and I did not see in the manual where the actual definition of X and Y in offset was, so I guessed they were percents?)
Problem 1: After thinning the glyph at one point, I tried to adjust the thinning amount. I seem to have reached a configuration in which running the offset curve with negative X and Y makes the glyph fatter, not thinner. Maybe I turned the glyph inside out somehow? I could probably start over from backups but am curious what is going on.
Problem 2: I tried this method on another glyph, intersection (U+2229) . Here, one corner of the glyph had a red circular highlight on it, and that corner was not moved upward by the offset curve. The right corner of the glyph raised a bit, so that after the offset curve, the left leg of the intersection symbol was lower than the right leg.
In the screenshots below, I will show the glyph before the applying offset curve, and then after selecting it (with select all) where a preview of what would happen if the offset curve settings were applied is shown: