I'd say around 1,000g you might want to move up to something bigger. Then they start too look kinda smushed in there.

When you upgrade, go for a PVC enclosure. it will be a little bit more expensive, but it will look cooler, and be less annoying to regulate temps/humidity. And it will be easier to clean! I have 3 boaphiles for my more space loving snakes, and they are awesome.