if you are going to trouble yourself to soldering a solid resistor then it would make more sense to solder A POTentiometer and have the flexibility of adjustable resistor settings.
That would be ideal for fine tuning but for being novice at soldering, wiring in a pot adds more difficulty than I am comfortable with. Tacking on a resistor to the sides of the existing resistor seems a little more doable for my skill level. And it's only $5 vs about $55 for the pots.
But, now that I think about it more, pencil would work just fine. I wanted to add the resistor so I wouldn't have to worry about the graphite potentially flaking off. But even if it did, having them hooked to a kill a watt would show a rise in electricity use. Then I would just have to check each voltage to find the culprit and just add more pencil.
go with a pencil mod - i did it for my bitfury cards (exact same regulator with 2 voltage-controlling resisters) and it works great. It isnt worth the effort and risks of desoldering pcb components and swapping in new resistors when a few rubs with a pencil works fine. tips:
1) get an artist pencil such as a 3B instead of a 2. It is a bit softer and leaves a tiny bit more soft graphite for a rub - a little bit easier to tweak the resistance this way
2) start small. Over time, the pencil mod will 'age' and slightly decrease the resistance even frther than when it was first applied, as the graphite is baked by the hot pcb. leave a little bit of headroom when you do a mod, and expect the resulting voltage to drift a little bit over a 4-12 hour period. (drifts up if overvolting and down if undervolting)
