AFAIK the yellow signs are "advice" rather than law. I make a point of at least doubling the "advice", visibility and governing speed limit permitting.
Why would you make a point of doubling the advised limit? I can't imagine your stopping ability is actually twice as good as average.
In other words, for no reason other than hubris/machismo, you're choosing to significantly increase your likelihood of wrecking your car (and/or others' vehicles) and possibly killing or maiming yourself (and/or others).
It just takes a bit of black ice, loose gravel, spilled oil, confusing shadows, distractions in the car (like spilled coffee) or outside of the car (like a bird or rock hitting your windshield, or a deer leaping into the side of your car -- to use examples that have happened to me personally), another distracted driver who has veered into your lane, and boom, you're done. They're done. Maybe the 12-year-old riding a bike on the side is done.
Sorry, this is an overreaction to a throwaway comment, but bad drivers who think they're good drivers are friggin' everywhere, and the resultant loss of life and limb is staggering.
FYI, the speed limit on that stretch of road is 35 mph:
https://maps.google.com/maps?q=Elk+Tree+Rd,+Woodside,+CA&hl=...