I have successfully installed C5 in a sub directory (cpanel addon domain folder), but Concrete won't use the addon URL, it continues to point all resources using the full parent domain path. I changed the C5 base_url to correctly point to the files, but I want the uri for all resources to point to the addon domain, not the parent domain.

Does anyone know how to use htaccess to rewrite the base url to use the addon domain?
I don't want to redirect...I want to rewrite the underlying url.
Change:

mainsite.com/network/newsite/

point to:

newsite.com