Issue with setup multisite network

[lefebvresam]

I tried to setup a domain based multisite network with separating the install files in a subfolder first.
After following the steps on the website I end with:

If I do exactly those steps I have 403 error when going to the main site.

When I insert (by trial and error) this line in .htaccess (now in comment #) the site is working, but the admin site is not longer working (404).

RewriteCond %{REQUEST_FILENAME} -d
#RewriteRule ^(/)?$ install/index.php [L] 
RewriteRule ^ - [L]

What is going wrong here?
What should be improved in the documentation?
What is the right config in this case?

[lefebvresam]

It looks like you have to overwrite '/volume1/web_packages/wordpress/install/.htaccess' instead of '/volume1/web_packages/wordpress/.htaccess', but when I create a new site with other domain and create a certificate, I get error 403. There must be still missing stuff in the head .htaccess file to make multidomain work. This is not documented.

[lefebvresam]

It looks like I have to disable the lines specifying a site in the main .htaccess, this is not documented.

<IfModule mod_rewrite.c>
RewriteEngine on
#RewriteCond %{HTTP_HOST} ^(www.)?saleconix.be$
RewriteCond %{REQUEST_URI} !^/install/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /install/$1
#RewriteCond %{HTTP_HOST} ^(www.)?saleconix.be$
RewriteRule ^(/)?$ install/index.php [L] 
</IfModule>