I don't see where you get that you'd only do incs over 5 rows.... or did you mean 5"?
First inc at the end of the next row, and every other row for 10 rows total - that's 10 sts so you'd now have 44 sts. Then inc on every 4th row twice - that's 2 more sts, for 46. You're also to inc at the beg of the 5th row and every 6th row twice which adds another 3 sts to get you to 49. This all takes place over 28 rows, not 42, plus the first 2 rows which would be 30 altogether.
And that does seem to be 5" worth. Do you have a link to the pattern?
sue- knitting heretic