It's rather strange that I always draw Elva with aristocratic straight backs and in perfect clothes. This is not entirely realistic.
In general, upright walking in them is a very recently acquired feature and they suffer quite a lot from this.
And there is a pretty strong tendency to keep the back at 45 degrees.
They never got rid of it by the way at all
Even after ~ 250 thousand years, Elva for the most part will keep this position, if this is not some important event or they are not photographed