Seems like all DFI LanParty P35 mobos work best with 266/667 and 333/800 Ratios. This is the case with me as well...folks on Anand Tech say that these give the best results considered the following:
* Raw CPU MHz per volt
* Memory bandwidth
* Memory/chipset latency
* Memory copy speeds
* Memory write speeds

And also that raw MHz and loosened latencies works better than smaller MHz with tightened latencies..