That hide size is actually perfect for that size snake. You will be able to use that for a long time to come still. Wait until they are under the hide and it is totally off the ground, and then wait some more, and then ''maybe'' you will need a bigger hide for your snake.
They do like a tight fit, huh? My little BPs are all lifting their (small exoterra) hides right now, but I figure they prefer it that way... weirdos.