Not sure how much help this will be... Spock was never in a cot with all 4 sides. She went from bassinet, to sidecar cot (one side completely removed against our bed. Then we moved her straight to a big bed, sorry I can't remember exactly what age she was....i know she was young for a big bed, like between 12 and 18months? Her bed has 2 height settings so it was low and we had a mattress on the floor for 6months, but she never fell out of bed. We kept the cot sidecared, and eventually a single bed side cared to our bed. As she got older we would go in to her less and less if she woke up and she would then come into us, and sleep in the single bed. Since quark has arrived, we moved the single bed away from our bed, but still I. Our room. She has her bed and her room and starts in there, and if wants to she is welcome into the spare bed. Over time it is happening later and later in the night she comes into us, some nights she doesn't come into us until morning time (after 7am in our house)
Like I said, not sure how much help....we just did a lot of consistency and perseverance....