Pack and Play Bedding, please help me!

Marie

We have decided to use a Pack and Play (Urbini brand) for our crib. It comes with a very firm and not so comfy mattress pad to sleep on. It says I can't put any extra padding or even a sheet on it! I can't see how this can be comfortable.

Do you guys use a Pack and Play and do you think using a slightly padded sheet or tucking in blankets around it would really increase the risk of SIDS?