I've got a normal ikea cot, with one side off, which fits flush against my bed, I have fasteners to secure it. With DC1, the mattress fitted completely level with my own mattress so no adjustment needed. Since then we got a new mattress for ourselves which is deeper, so it is higher than the cot mattress. I bought a new cot mattress for DC2, due imminently. I bought a deeper mattress, with the intention of making up the difference by extending the legs (DP is good with DIY and can safely rivet extra lengths onto the legs). However, when I've put the new cot mattress in, it is only 5 cm lower than my own mattress. Can anyone say if it would be safe as it is, for a newborn-approx 18 months, which is the likely length of time co-sleeping.
My own feeling is that a 5cm ridge of my mattress won't affect a small baby who can't move, and by the time it's old enough to roll into it, 5cm will be shallow enough to not make a difference. But then I worry that they will get their face smushed against that tiny bit and get stuck.
I'm probably safer just extending the legs by 5cm anyway aren't I?