I tried your bios settings for 475 and the fsb is not stable on my board with these settings. As for vcore being the problem, my system is (at least) 1hr Prime stable at 4.2GHz with only 1.318v in bios so I didn't think I'd need anything like 1.3 vcore for 4.1GHz, but I'll bump it up and see what happens...

I'm working with the 8.5 multi because I want high memory bandwidth, I need too much vcore for 4.3GHz and it's far too hot.

I'm also going to try tuning the clock skews and GTLs to see if I can prime for any longer - with CPU and NB skews at Delay 200ps I can prime for 15mins, but set to Auto the PC freezes within 1 minute