Can I turn any simple (no cables or other fancy stitches) pattern for a watch cap to double knit, by doubling the number of stitches cast on?
@Mike does a lot of double knitting so he can probably answer your questions. I’ve tagged him.
In short, yes. Including cables and fancy stitches.
You may need to figure out your gauge changes. Generally your double knitting will be larger. If you make one side all color 1 and the other all color 2 so from your view you knit all one and purled all 2 you may notice a pretty drastic size change between the sides so knit the one you want on the out side on the inside (this is mostly how even you are between knits and purls).
2x2 ribbing won’t be as stretchy, mostly the low measurement side, it won’t pull together as tight as single sided 2x2. Whether you make the ribs nestled or opposing changes how it pulls together and gauge.
So with some trial and error as far as gauge yes it can be done.
Thank you so much for this very helpful reply.