moving to crib- how to elevate baby's head?

ok. dd is ready for her crib, and i guess i am too :) she is sleeping through the night, only waking once or twice. when she wakes she usually cries out once and goes back to sleep on her own. she's falling asleep on her own at night in her bassinet. and since she's 6 months old and approaching the weight limit, it's time to leave the bassinet.
the problem is, that we have her bassinet inclined to relieve congestion. anytime we lay her flat her nose immediately stuffs up. she constantly wakes herself up because she only breathes through her nose. our bassinet is fantastic because you can easily gently raise the head (it also converts into a seat, so we just lift it 1/4 of the way to the seat position). so what do i do in the crib? i know people how put stuff under the mattress to make it slightly inclined, but then the baby just slides right down to the bottom of the crib. i think that would happen to us because she needs more than just a slight incline and the darn mattress is so firm she won't sink in to it at all. i read online reviews of sleep positioners and wedges, and almost all reviews say that the baby didn't stay on it. dd is 6 months, but she does not roll back to belly. i am sure she will be soon though. she has always been a back sleeper, as we never tried any other positions. any suggestions?

[CYW]

i think there is sumin u can either put under the matress which would be hard to do...or under the fitted sheet...

[marra315]

you can get a wedge that goes under the matress in uk and we are advised to have the baby sleep at bottom of the cot as the feet are against the foot board and cannot slip down under the covers and suffocate . x x

[kcs08]

We put DD in her bouncy in her crib-she slept in that for 3 mo due to reflux until she started rolling over in while swaddled at 3 mo!  Then we tried the towel under the mattress but she rolled all over the place sometimes she was sideways or even upside down.  She just had to get used to laying flat. :(

[tiredbuthappy]

it's not that she's not willing to sleep flat. it's that she can't breathe that way :( her breathing rhythm gets interrupted as her nose gets stuffier and she ends up gasping for air in her sleep through her mouth. as soon as she catches her breath, she goes right back to trying to breathe through her nose and the whole process starts all over again. the humidifier helps a little, but not enough.

[newbie2b]

Hey. My daughter had acid reflux and we had to keep her elevated. She slept with us until she was aout 6 months, then back to her crib she went.  I had bought one of those stupid wedge things with the hopes that she would sleep on it. It didnt work, she would move all over the place.  So what I did was, took the wedge (foam) and stuffed it under her mattress.  This way her mattress was at an angle. It worked just fine.  If you dont have that wedge, use a pillow, I'm sure it would be the same thing.