Technical Question: totally clean install of Win8Pro upgrade? [UPDATED]

I want to install the Win8Pro upgrade onto a securely erased SSD (a factory reset for optimal performance). Obviously the upgrade needs to see a previously activated version of Windows before it will continue. If I put in a second HDD (disk1) and installed Windows 7 on it, I should be able to install the upgrade to the pre-partitioned SSD (disk0). Can anyone think of problems with this approach? I can't... but... Cheers (PS - I'm not looking to dual boot, just start the install onto a completely fresh SSD)