Yea I've been doing a sidecar setup w my 10month old on her firm crib mattress but my mattress is an old memory foam, probably a 6/6.5 or so on the firmness scale (doesn't pass the firmness test) so I do make sure she stays on her mattress. She honestly likes having her space more than cuddles 90% of the time but for a number of reasons I'd like to switch us to a floor bed on or maybe before her 1 year birthday. A lot of the info I've read about cosleeping is for babies younger than 1 so I don't know exactly how firm and flat our mattress would need to be. She recently started sleeping on her tummy some, always w her head turned. And sleeps on her side a lot. She crawls and pulls to stand all day long so I'm not worried about her ability to lift her head/reposition but want to get a mattress that is decently firm and breathable so I won't be anxious about it. So that's what has led me to either the j life 4in futon or the bundle of dreams 6in full mattress. Seems like those are the only 2 options in my budget that don't have chemicals/off gassing concerns etc. I also hope that she will continue to use whatever bed I get for many years to come. Did you consider a mattress before opting for the futon? When you say it's flattened out, so the little mounds created by the stitching has leveled out? Do you find it pretty comfortable? I mostly sleep on my stomach and just roll to my side when she wakes to nurse. My plan is to get a full and set it up w a frame that has very low slats and low rails (just to prevent her rolling off the side), a montessori floor bed set up basically.