So my mum sent back the Dogosaurus sweater because she couldn't get her dog inside of it. I opened up the chest and made a gusset, knitting it out of the same yarn but on bigger needles and garter stitch. As well I removed the sleeves and added one round of double crochet to clean it up. It may be tough to decipher what I'm taking a photo of, but here's the new belly:
The photo actually makes it look like I've just opened up the centre seam and what you're seeing is the inside of the back. (My thinking was that when the dog has the sweater on, the garter stitched tummy gusset will look more like the dinosaur's scaly tummy. Oh who am I kidding? )
Here's the link for a photo of the original sweater, with the pattern.