I have booked the cheapest possible fare HEL-CDG-TUN and back. I have no status with Flying Blue.

While I have the right to a full-size 12 kg carry-on, the AF website stated something along the lines of them force-checking the bag at the gate if overhead bin space is scarce. How often does this occur in practice? I know US airlines do it, and those affected are in the last boarding groups. Does AF do it routinely? On full flights only, or...?

I will only have this one bag, so I will have my laptop in there, as well as medicines etc. I cannot have it checked, especially with the reputation CDG has about losing bags. Is there anything I can do to avoid this?