If you haven't already, check out Seamwork Magazine. It's a monthly publication by Colette Patterns with some fantastic downloadable patterns and good articles. I wrote one for this month's issue on working with double knits.
You can read all about it here:
https://www.seamworkmag.com/issues/2015/01/working-with-double-knit
You can read all about it here:
https://www.seamworkmag.com/issues/2015/01/working-with-double-knit