Best 301 Redirect Method when using Domain Mapping

Hi -

Posted this request first in Plugin Support for Domain Mapping, and got one reply that the person answering did not understand why we were asking the question, then someone closed the thread. My question is NOT answered, so I will try again here, with somc elarification

We have a mutli-site setup where we have domains first set like this: xyzcompany.ourTLD.com. CLARIFICATION: Clients may stay with this for 1-5 months before switching via the domain mapping to a subdomain of their own website. During this time period, they gather "SEO juice" for this initial subdomain and when updated via domain mapping (see below), we need a best method/plugin to redirect from the old subdomain to the new.

We are using the WPMUdev Domain Mapping plugin at times to later change the blog's subdomain to: blog.xyzcompany.com.

So, we are after the most efficient 301 redirect solution to affect this change and that will work with the Domain Mapping plugin.

CLARIFICATION: If a client's site was listed as xyzcompany.ourTLD.com, and changes to blog.xyzcompany.com -- does the Domain Mapping plugin handle all 301 Redirects in such a way that Google transfers accrued "SEO Juice" (ranking) to the newly mapped subdomain?

I am aware of htaccess, php function, and plugin solutions and have read a bit about these here on the forums, but need to know best recommendation for the above configurations with Domain Mapping in place.

Thank!
- Scott