Been putting my chips as far as I can since my first overclock on a Cyrix 586 ... never lost one to overdoing it yet.
I'm probably just being overly cautious tbh I usually am and especially with a chip costing this much...

I've found with CPU overclocking you tend to get loads of MHz for very little voltage increase and then hit a wall where you need lots more volts for very little increase, I usually just stop at around the wall and try to get things stable. I've always been more concerned with temperature and stability rather than all out performance.
What Cinebench score do you get at 4.7ghz out of interest?