Just a quickie - for those of you that have already received them, how're you finding the stay-dry flips? We got two this morning and I LOVE them. They're so trim... but is just one insert enough? It doesn't feel bulky enough to hold much wee. I soooooo want to buy more (and want to get in there before the BOGOF offer ends) but don't know whether to risk it or not, or wait till we've tried them properly and risk the offer ending.