I'm wondering if anyone can come up with an alternative to using a "#include file" command. The situation I currently have is thus:

On my primary domain, I am attempting to use a server side include to insert the text from a file in a subdomain. The reason for this is that the subdomain is run by someone else, and I'm not about to give them full access to the entirity of the domain and tell them to only edit their folder.

So anyway, I've been attempting to use:
<!--#include file="/var/www/vhosts/zebeth.com/subdomains/subsector/httpdocs
to insert the text from the subdomain (called subsector) into the homepage of the main domain. It's been constantly failing with the error "[an error occurred while processing this directive]". The error log gave the following:

unable to include file "/var/www/vhosts/zebeth.com/subdomains/subsector/httpdocs/ztest.txt" in parsed file /var/www/vhosts/zebeth.com/httpdocs/planetzebeth/test2.html

Long story short, after much testing with the server support, they concluded the following:

The server is having suexec enabled and so the website code running under cgi or ssi will be running under the identity of the corresponding user.
See http://httpd.apache.org/docs/1.3/suexec.html
Main domain and subdomain are having different suexec users and so
is working well which is accessing the page from domain itself.
URL http://www.zebeth.com/planetzebeth/test2.html which is your code is taking from the subdomain which doesn't work because of the suexec mode.

So from what I can gather, I'm basically stuck trying to go down the '#include file' direction. The server provider isn't about to change base permissions of an entire server for one random website taking up a very small portion of it.

Thus, I'm looking for possible alternatives that would bypass this suexec problem. I currently have it running through an iFrame, which sucks in general, the least of which is not the non-variable height.

Any help you could throw my way would be greatly appreciated.

If it helps, the webroots for the site are:
Main domain - /var/www/vhosts/zebeth.com/httpdocs
Subdomain - /var/www/vhosts/zebeth.com/subdomains/subsector/httpdocs

And if it's of any value, my 'test' page is at http://www.zebeth.com/planetzebeth/test2.html .