Questions about Joule Performance Storm

The chairs come from the Middle Kingdom and go through Swiss quality control. I first tried to sew them together myself, but quickly realised that I have little talent for it :)

Stitch area is 39cm, whole seat with side roundings (see 3rd picture) 59cm. Fits me (male but slim) very well, but we are not all built the same.

This information is not provided by the manufacturer, the only information provided is the height of the seat: from 48 cm to 57 cm.