Just bought a new bed for dd who is 7. It's a mid sleeper with desk and she loves it. I didn't however, buy a new mattress and just chucked her perfectly fine Ikea one on the new bed. Just been talking to a friend about the new bed and she mentioned that cabin beds should have a different height mattress. Did a quick google and read the small print of the bed I bought and it does indeed say that the mattress should be 15cm high. Turns out Ikea one is 20cm. Friend was horrified by this and basically said I was putting dd in danger every night! Is it that bad?! Really could do without spending £100+ on a new one for the sale of 5cm....