As a general rule, the best way to resize amigurumi is to change the yarn weight and corresponding hook size. To double the size of an amigurumi, use a yarn
pocket yarnlings
Knitting and Recommendations. How Computers Think: Part Three, by Simon Carryer
Little World of Whimsy
Amigurumi Made Easy
Little World of Whimsy
How to Become an Amigurumi Designer in 8 Easy Steps
How to Become An Amigurumi Designer in 8 Easy Steps - Elise Rose Crochet
How to Become An Amigurumi Designer in 8 Easy Steps - Elise Rose
Resizing Amigurumi – PlanetJune by June Gilbank: Blog