clips do not hold duvet firmly so it will still be kicked off, especially after a little while when the elasticated bit loses some of its elastication. we used them but found the duvet just got kicked down the way rather than sideways and as it got kicked down it got a bit twisted and when he did wake up he couldnt pull duvet back up himself.
ds is 5 now, but never thought about tucking duvet in sideways, could you put a blanket at the bottom to cover feet if too short?
I posted about these on a different thread yesterday as I bought these for ds but took them straight off as they worried me a lot after I watched ds with them. I'm lazy so have copied and pasted it!
He came straight upstairs and asked what it was and started to pull at the duvet whilst in the bed. This stretched the elastic up from under the mattress, surprisingly far too. He thought it was a great game to stretch and twang it whilst underneath it. I took it straight off as I don't think I could have slept for fear of him doing that and getting his neck caught. I may have been over reacting but it looked really unsafe with what he was doing with it.
I know they must have passed safety standards but it looked worrying to me once my ds got his grubby little paws on it!