If your hosting is Medium Trust hosting, you cannot change it to Full Trust from Web.config. It does work the other way where if you are hosted in Full Trust you can set it to Medium Trust from web.config because that is more restrictive, but it will not let you configure it for less restrictive than what th ehost defines for trust level in machine.config.

The mojoPortal full trust web.config does not change it to full trust it just has the right settings for use with full trust.

The same is true of our main Web.config, it has the right configuration settings to work with medium trust but it does not control the trust level.

If you are hosted in medium trust you should not try to use the full trust web.config file

The main thing you need to support multiple sites by host name is a dedicated fixed ip address that you can point the host names to from your DNS management. If you can reach your site directly by using the ipp address instead of the host name then you know you have a dedicated ip and it should be able to work. Without  a dedicated ip address, it would require your host to create host headers on your site for the additional host names or they will never resolve to your site.

Hope it helps,

Joe