Doncat, i have to say i have just put up my new pen, (the silver one in the left of your pics... Marble the little dear,jumped over and out the first morning. We're not sure if it was because my son went to get her veggie treat BEFORE he let her out for the 1/2 hr play.
Have yours ever jumped out? I havent put the net on as i have it up as rectangle rather than hexagon.
I can still get the net on as a rectangle.... I have it as a rectangle when I'm cleaning round it, the net just stretches a bit. Comet has had a spinal problem and is tiny so I doubt its possible for him to get out, the net is there as a precaution really, but I also have the same pen around Bob's indoor cage and he mysteriously appeared out of it once, but never again. So yes it is possible. You could alway get some gardening net and make that fit.