This is our net in the background. It is quite stable. As we are both technically challenged we had it made by a professional when we first got the cats. Around here you can ask in the specialised cat shops they know people. It was not too cheap (ca. 200 US$) but we have it now 7 years and it will work at least some more seven.

It's fixed at the roof over the balcony.

However here it depends whether your owner community allows it. Your landlord can forbid it.

Looks a little like a football goal but Tigris cannot suffer the destiny of his uncle.