No power for a kws?
The build for the VIper you posted had no power priorities set on it. if you don't set priorities for modules you're missing out on a great little tactical part of ship building.
For instance, always turn off the cargo hatch (and set to level 4 or 5) when not using it, and anything else you don't need to have on while you're doing what you're doing.
Afmu? - only turn it on when you need to use it as very power hungry (priority level 5 so that when you switch it on it won't turn other important stuff off)
Scoop - level 5. It aint helping unless in supercruise. Same goes for interdictor too.
Play around with priorities like this and you can make it so that all your low level stuff that isn't needed when you drop out of Supercruise can then, just be left to switch power off when you deploy weapons.
You'll find you can then often run a lower class power plant than the stock level.
Switching stuff off also means you're using up less fuel
Good Tip!
will have a play about, cheers 