I have had a few people mention that they were having trouble getting the waistbands of the Little Fire wooly patterns loose enough to have enough stretch, even when using a larger hook for the foundation. I have found the answer...the no-chain foundation!! If you go here No Chain and scroll down to the bottom of the page, you will find instructions for doing the No Chain Double Crochet. Work this technique to length (one less dc than the number of dc's called for in the pattern) in place of the foundation chain and first row of dc in both Little Fire Patterns.
I tried it out myself on the Pirate shorties I just made for my son (incorporating a little stranding for a bit of fun) and it worked out fabulously. There is a small V at the join when following this technique, but it is easily stitched closed with the tail. The resulting stretchy waistband top is wonderful!