htaccess 302 redirect - seamless hidden url

Greetings,

I have a base magento install on abc.com and have setup multi-sites and stores for different domain names.

If I setup xyz.com domain and set it as an alias to abc.com the site works as expected. Magento recognizes xyz.com in the address line and treats the site as if it were xyz.com. However, I cannot bind an SSL cert to this domain as it doesn't exist as an entity but as a pointer.
Therefore I'm under the understanding that for xyz.com to be served from abc.com and have xyz.com SSL cert I have to set it up as a site and use an htaccess file. I'm pretty familiar with htaccess files and have had many other setups work successfully simply using a 301 redirect. This though changes the address in the address bar. This is bad as magento will not know which site to serve up, so I figured a 302 redirect would work well.

I've done some extensive reading and from what I gather an external redirect such as xyz.com to abc.com would be would be defaulted to a 301 redirect.

How can I redirect to abc.com as xyz.com? I have full access to all the sites, with the only exception being that I cannot edit httpd.conf, hosts.conf or install new modules on the apache install.

FYI, I'm running the sites from RackSpace Cloud Sites offerings with a dedicated RackSpace Cloud Server for the database.

Please could some help.