I've had to double check a few times the year when the OP made this post and since its "2018" it makes absolutely no sense to mine SC with GPUs now. Its basically all dominated by ASICs. Even with free electric its not worth the extra heat of dual-mining SC.

SC was worth mining back in 2016 before there was pools and you were forced to solo mine it , when you found a block you got like 250,000 SC.

Second time when it was worth mining was in June 2017 by dual mining it with ETH, I think with an RX 480, you could of made an extra $2/day/per GPU on top of your regular ETH mining income.

Now it doesn't make any more sense to mine SC. No idea why this guide was even created.