two 2.5" drives INSTEAD of one 3.5" HD (apple fusion drive)

Hi Guys

Maybe I´m being stupid here so I thought you could help me out:

I want to get more mileage out of my iMac 21" 2010 and when I heard about fusion drive ( http://www.anandtech.com/show/6406/under... ) it hit me:

Pull the 500GB 3,5" HD and swap it for a 2*2.5"to 3.5" adapter tray (like this one http://www.newegg.com/Product/Product.as... ) and install a 1TB 2.5 HD plus a 128GB or 256GB SSD in its place.

Obviously I´d need a SATA Y-cable to connect two drives to the motherboard (or is there a spare SATA connector?)

Anybody tried this before?

Any practical theoretical roadblocks?

Would love to get your input.

cheers

Matt