This pattern can be found in my 2016 book Double or Nothing: Reversible Knitting for the Adventurous.
In my first book, I started out with two relatively large projects. The unstated reasoning for this approach is that it’s much easier to do advanced double-knitting if you have the muscle memory for standard double-knitting first. A large piece will give you this muscle memory in a way that a potholder never will.
To that end, I’m starting off my new book with another large piece -- this time, in the round. The repeat for this pattern is insanely huge, but I’ve worked in an ingenious little trick that makes it possible to chart the whole thing on two facing pages.
As charted, this cowl is 42” around and 8-12” tall. At the largest size, the finished piece uses 10.5 oz of yarn in total, so you’ll have plenty of yarn left over — or you can make it bigger, I guess.
Theoretically, 3 repeats around would be 15.75 oz, which you’d still have more than enough yarn for. However, this would make the piece 63” around. If you want it smaller, one repeat would be 21” around but the repeat doesn’t allow for more granular sizing so if you need it between sizes you’ll need to change your needle size or yarn choice.