- We run a main website ("MAINSITE.com")
- I want to start several subsites off of the same server via subdomains (we'll call them "SUB1.MAINSITE.com" and "SUB2.MAINSITE.com")
- I want to purchase some extra domains nice and cheap that redirect to the subsites as shown below:

www.BLUEWIDGETS.com ----> SUB1.MAINSITE.com
www.REDWIDGETS.com -----> SUB2.MAINSITE.com

Now, I do worry about the search engine placement of MAINSITE.com -- I don't want to harm my good ranking. The subsites I could care less about, don't even care if they are in the SE indexes. The domain names will be given out via direct mail only, any links to the subsites from the mainsite will just address them by subdomain. The domains are just for aesthetics in the direct mail marketing and also for ease of conveyance when talking with potential clients.

None of the content will be an exact duplicate (except general forum text or whatnot)

I want to pick up the domains cheap and that eliminates purchasing them through my hosting company. Due to this, I am stuck with using the forwarding of whichever domain company I register with. A certain one is nothing but 302 redirects and the rest seem to not have a clue what type of redirects they utilize.

I did find one that just uses a frameset to display the sub-sites and still show the extra domain in the titlebar.

Is that a safe way to handle the redirect without endangering MAINSITE.com?