I set the CAS to 3 and put all the other settings to AUTO. My motherboard came up with the setting 3,3,3,8 2T which booted fine at 285Mhz and appears to have a very similiar latency to 2.5,2,2,5 1T at 237Mhz but with a 10% boost in bandwidth.
I ran CrystalMark and got a score of 62369! But I'm dubious about the score as one of the tests was 91% higher than I previously was and another test gave me 5% higher than a previous run.
If I get time I will do some more testing on CrystalMark to see if I can identify this problem further.