Hi, we have a tall 7 month old who can stand themselves up and their head is higher than our crib side on the lowest setting. They are constantly using the crib sides to walk around and have started to try to reach over the crib. I'm worried about them falling out in the night as they're so active. I can't find any cots that are closer to the floor or that have a gated side. Is it safe to have a mattress on the floor? Or transition to a Montessori style floor bed so young? Thanks

Red Nose recommends that once a baby is attempting to climb from the cot & looks like being successful, then it is time to move to a bed.
This usually occurs between 18mths to 3 years. (sometimes earlier)
However, 7 mths may be a little early, but it is really a matter of weighing up any potential risks.
I understand that there are some families who use a floor/toddler bed from a very young age.

The risks are related to what areas your child may have access to now they are no longer in a cot.
https://rednose.org.au/article/making-your-home-safe-before-moving-a-child-from-a-cot-to-a-bed
https://rednose.org.au/article/where-to-sleep-a-child-who-has-moved-from-a-cot

Have a look at Red Nose “Cot to Bed” brochure - https://rednose.org.au/downloads/RN0407_22_Cot-to-Bed.pdf