I want to buy a summer cot bed duvet for DS, but can only find 4.5 tog duvets for his cot (he is 14 mos, btw, and okay to use a duvet.) I've read that 4.5 is the highest you should go for use in a cot. That's what we're currently using, so think I should get a lighter weight one for the summer. Point my in the right direction if you can. Thanks!