Sensen, I guess it is just that you typed it wrong, though 5x112 gives 560.
Anyway, it will perform better than
[email protected], if your components can take it (if you can get into windows without blue screens, it is a good start). Remember that increased FSB means increased AGP and PCI bus speeds.
I have a config similar to yours, K6-2 500 with MVP3 based mobo.
I know 500's are usually stable at 560 2.5V, it is quite weird that yours cannot take it at a lower voltage.
That is why I guess K6-2's have a rather bad overclocker image: it is a russian roulette, you can push one chip to whatever you want to, while another one (same specs) will be a real pain.
Mach 3.5 is right, you can push the voltage to 2.6V, that's the design limit AMD says. You can give it a try (be sure to have some rather good cooling stuff, and a bit of thermal paste) and after the "burn in" try to lower the voltage.
Otherwise, accept your fate...