DPN and Circular legwarmers

Pattern: cast 40 sts onto dpns, knit the ribbing, then slip the sts to a 16 inch size 6 circular needle.
Won’t 40 stitches be stretched ridiculously, across a 16 inch circ?

Pattern is in Knit Grrl, pages 58-59.

What is the LEAST amount of stitches, using red heart yarn, regular old, everyday red heart yarn, that a person can knit, comfortably, on a 16 inch circular?:hmm:

It depends on the weight of the yarn and your gauge, but 40sts should fit. When I make hats on a 24" I can decrease down to about 60 sts before it gets too tight.The cast on edge would be too tight to fit them on, but after you knit an inch or two (the ribbing) the outer edge that you’re knitting on will be a little looser, though not enough to be stretched out.

I don’t have the book so I can’t look up the pattern. Are you substituting the yarn called for in the pattern? Is the Red Heart the same gauge as the one in the pattern (or at least close)?