Beanie for Dreadlocks - HELP PLEASE!

So I am new to circular knitting and am in general a pretty beginner knitter but learn really quickly! As a gift, I am trying to knit someone a beanie for their long dreadlocks. My question is, how many inches tall would you advanced knitters out there suggest the rim of the beanie be, and should I be adding stitches after the rim to make more room for the dreadlocks as I knit a longer beanie, or just simply continue knitting and make the pattern longer before i begin rows of knitting stitches together to cap the beanie and hope my yarn will have enough stretch for space for the locks ??

Welcome to the forum!
There are different ways of working these hats. Here are some ideas from Ravelry.

You might be able to look at some examples of messy bun hats for ideas too.