1 1/2 yrs ago our 10 wk old Goblin was on top of a half wall in the living room, the other half of which dropped down to the entrance hall in front. We had not had a kitten in a very long time, and while we were careful about what we could think of, obviously should have been a bit smarter (plus we somehow think cats can't hurt themselves when they fall, even though we do know better). Anyhow, he did slip off, fall asleep, something, and next thing we knew he was down (on tile) and crying just like a baby! It just about killed me to hear it and I can honestly say it was the most traumatic thing I experienced in a long time.. took ages to stop feeling so awful every time I looked at him. He had hit (his nose I guess) a little shelf on the way down, and did have a sore, red nose, which a cold compress fixed up pretty quickly, but until I was sure he was more or less ok, and until I could escape with him to a bathroom, from our older male cat whose instincts told him to go for the kill (even though he was our babysitter/friend/daddy otherwise) when he heard the cry, I just felt about as bad as a person can and still keep going. You absolutely must find some way to keep yours from getting through that thing (thank goodness he's too small to jump so high). What about some very inexpensive chicken wire (watch out for sharp edges!) or strong fabric, etc. wound around - and remember they can push through incredibly small spaces. Maybe just keep him away til he's a lot older because even adult cats, who have great reflexes and conditioning, can have accidents if being chased, or whatever.