I suggest you give them to me

You can't split games drives on Steam, it's one folder location. My Steam directory would require about a £500 SSD, so I don't actually have it on there (Raid for me).
Anyhoo... Err... It's pointless RAIDing a SSD (no trim support) at the moment. So I'd boot off one.
I did have Starcraft installed on my SSD, and did notice it loaded quite quickly. Maybe use one for Origin for BF3?
Or a second Steam install with just your preferred games on it... that might work?