Those directions are fine, but a little out of date.

Stern changed the 520-5254-00 step-up board and DID NOT CHANGE THE PART NUMBER. If you order from PBL, you will probably get the new part. It requires 20V and 50V, so you'll have to tap into that, too.

If you have a metal-head style game (Star Trek and forward) I have no idea where you're going to mount the knocker in the head. (On my WPT I mounted an old Williams knocker in the head and IT SOUNDS GREAT.)

Mount the knocker so that it isn't near the end-of-stroke when it contacts the wall. This is how Williams did it, as far as I can tell, and it sounds better.

If you are mounting this in a game without magnets, there should be an unused 50V pin in J10, the high-power output from the driver board in a SAM or Whitestar game. There are plenty of extra solenoid ground pins, which is a little cleaner than using earth ground. An IDC punch-down tool is very useful for this.

Or, you can do it the way I did it on my Simpsons and tap a coil under the playfield. That's a hack, though. I can't recommend it, but it will work. That's what the directions above discuss.

My notes are here: http://ty-ffasi.com/installing-a-knocker-in-sterns-world-poker-tour-pinball/ but these aren't complete directions.

[edit: Iron Man VE has a new head and magnets. I think I would use mid-line taps to get 50V, and mount the step-up board in the body cabinet. If there's a shaker motor there's 50V in the cabinet and that may be a big help.]