good question Madmax, and i am interested in the iframe thing because just started one new my project where my content will be in iframes..
About the hardlinks i am doing it with custom script. From the admin interface i just add the linktrades for the proper domain, and with php includes i call the necessary file to show the linktrades for that domain. From one admin interface i operate all my domains.This is better than iframing. Also i made my apache to parse html files as php, so my pages are .html which is better for SEs. For now i can say it is going pretty well. If you need such a script i have one ready for sale, already have selled it to couple of webmasters. If you are interested contact me...
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