WEll since most memory is unique put the loosest timings you can then boot and run memtest86
then slowly tighten em up a bit , each time running memtest again.
when you see errors back-off a bit and run memtest again (this time for al ong period of time) and if no errors crop up , keep it there...
This process takes a bit of time but its is imo the best way of getting the highest, most stable memory speed