that is true - but i think the resources bar or properties would reveal the real source that way, so i guess - mirroring is the way to go and i will try to make the site - that the domain lands to re-act, in a different way - if the visitor arrives from the secondary domain.... instead of the real one.
otherwise - it does what i want - conceals the source of the files on the other sites, so your help is greatly appreciated.
Just one final Q - is it completely - impossible to meddle with the Cname and A records on dreamhost ?! (just for some other things i might want to do)