I think 1.43-1.45 is about the max for these chips under the currently available air cooling. I'm keeping it at 1.48v @ 4.3ghz at the moment and one core goes to around 64C in Orthos while the other jumps between 58-61C. I've heard that the max recommended temps. for these was around 65C.

I throwed some Orthos at it @ 1.55v @ ~4500Mhz. Cores jumped straight to 75C and they we're surely gonna get hotter then that, maybe 80C