you could probably get it to run at the loosest timings the kits offer, but that would be pointless.
Its almost running at 1333Mhz / CL10 (both kits are 1600 / CL9) but suffers the occasional instability - was hoping for something more "2014" than "hey, it's the dark ages how silly of you to expect technology to work, you were lucky last time!".... disappointing that a board this advanced can't cope with 4 DIMMs of the same voltage, speed and timings just different capacities - why have 4 DIMMs if they're not really all usable. Ho Hum.... guessing one of the kids is getting 2x4GB DIMMs for Christmas
Thanks for the replies guys...