Hello,
before doing so, I have done some additional testing.
But first I done the following:
I removed some proprietary CSS-code I added (in an earlier attempt to have a wider body (no proprietary CSS-code remains now)
I also restored the file /templates/ja_purity_iv/html/com_content/article/default.php to its original state (a change that was suggested by "dominic" in order to deal with the "Read more/Read next" issue (see another issue of mine)
I took the original JA Purity IV template style, made a copy of it and defined that as the default for all pages of the website.
Additionally I chose the setting "Fluid" and changed the width settings of the 3 parts of Main Body to "auto". See hereunder
As a result you can see hereunder that the page only occupies about a half of the total width of the screen (the indent after the first paragraph is caused bij the "Read more/Read next".
The I made Cassiopeia again the default template style for all pages. And the the page occupies the whole width of the screen again. See hereunder.
If needed I could provide the html-code of both pages (JA Purity IV and Cassiopeia)
Kind greetings,
Hendrik