Convert a pattern - need help

Here’s the pattern:

1 skein wool ease thick & quick (Lion Brand)
US 15 needles

CO 15 sts.
Row 1: *K3, sl 1; repeat from *, end k3.
Row 2: K1, *sl 1, k3; repeat from *, end sl, k1.

I want to convert this to using size 11 US needles cause the yarn I have is less thick than the above. BUT when I try to CO a derivitive of 5’s, it doesn’t come out the way it should. How many should I CO to make this work?

Because the sts aren’t a multiple of 5, but 4 plus 3. So you’d need 19 (4x4=16+3), or 23 (4x5=20+3). Or maybe 27.