I have a pattern for a children's lightweigth jacket that is knit in Berroco Sox yarn, gauge 30 stitches = 4", on #2 needle. Figuring that might take forever, I was wondering if I can change the gauge to a sport yarn or DK weight, and therefore use a larger needle? A sport yarn weight would be about 22 stitches = 4" on #6. Would it be a simple matter of figuring our the math? How would you figure yardage?