Hi guys, I'd like to install Yosemite on my 2011 air, but I'm not quite brave enough to go all out and install over my current internal mavericks OS. I have a usb3 external SSD that I was wondering if I can clean install Yosemite onto it and then boot from that for the time being to see if I like it? I realise my Air only has usb2, but its more to have a go at using the OS for a few days before doing the update properly. How is best to go about it? Thanks very much!