Note: Not all pencils are created equal. A generic #2 pencil from Office Depot wouldn't get the voltage over 1.13 volts. A good ole' fat construction pencil from Home Depot worked much better for me.

Remember to always test the first cap (C17, I think), because it will show the highest voltage, in case you over-pencil it.

As far as my experience: I have 6 S1 Antminers, and none of them like the 418 MHz setting. HWE rates were 4.5% - 5.3% with hash rates around 210 GHs even with the pencil mod. At 393 MHz (5f05, 36) I was getting .85% - .90% HWE before the pencil mod, but the mod actually lowered it to .45% - .51% across the board. Hashrate has remained at 200 GHs. I don't have a killawatt, so I have no idea on consumption.

edit:to the OP, what firmware do you run?