I have improved a fair bit since I posted the initial SU of the chevalet. In fact it was my very first attempt and it was, in a word awful. I may not be a pro yet but at least this SU can be pulled apart and measured.
There's no need for further explanation except top say that this chevalet as drawn can be set up for a seat to blade height from about 22" to about 25". That should accommodate almost everyone.

EDIT: Here's an even better one with a "dimensions" layer.

Thanks for looking

Paul