I wouldn't call you obese, Dee! And yeah, I'm inclined to think that the 'overweight' thing would depend on other things, and not a risk on its own, as with many other things it would be subject to combinatorial factors.
We use our duvet, it is made of natural fibres. Our mattress we chose for health reasons way before DS was conceived...it's made of latex and it's a futon, so we don't have synthetic fumes interfering with our sleeping. In his bassinette I used a latex piece that I cut myself.
Like I've said, where you have your wits and instinct about you, I don't think you need to refer to guidelines to feel you are doing the right thing. I've never asked our caregivers about how we co-sleep or feed and I know DS is doing fine as fine can be. I won't say 'common sense' cos that's non-existent and that's why we have 'guidelines'...for those who lack trust in themselves.
Well, Dee - your kids and my kid are theoretically dead, then!