Sorry when I say 1:1 with a bit of overspill i mean 4:5. 5:5 = 1:1 so 4:5 = 1:1 with a bit of overspill. If that makes sense?
eva: Yes I see this... NOW!
That does require more Vdimm though than 1:1 with tight timings regardless of DDR2 sticks on market at moment.
Unless of course you're running G.Skill HZ's.

All my tests were run with 1.9V VDIMM regardless of timings. 1.9 in BIOS is about 1.94 actual.