22mo starting to climb out of crib, what should I do?

Hi

My 22mo babe has started showing signs of trying to climb out of his crib. I think he got the idea from watching his 7yo sister climb in and out to play with him.

He hasn’t climbed out by himself yet, but he was able to hang onto the rail with both legs over it (imagine a caterpillar on a stem 😂). He wasn’t wearing a sleep sack at the time because the kids were just playing in the crib.

He’s been sleep trained with Ferber since 6mo and has been doing pretty well with his bedtime routine.
My question is what should I do about the climbing situation? Should I remove the lowest part of the crib and put the mattress on the floor inside the crib, or use a net? We’re really not ready to move him to a toddler bed yet.

Would love to hear what other people did when their toddler started trying to climb out!