Can I ask did you build your catio from scratch or did you build it from one of those catio kits? I've been considering putting one on my balcony for the cats but I'm trying to figure out what options are out there that people recommend
I built mine from scratch and it's actually primarily an aviary--Arson and Larceny get the main space when the weather is above freezing at night; when it's too cold, they move into the house. Malice and Vice get the whole space when the doves are indoors, and when the doves are out, they just get the little "airlock" area that exists to keep the birds from having a straight shot to the sky when I open the main aviary door.
The prefab catios are a great option if you don't have the skills or tools to build one yourself. Depending on the shape of your balcony, you may actually be able to enclose it entirely. I can't recommend a specific product though.
If you're able to build something custom, it's likely to be less expensive than the purchased options and you can probably go bigger than most commercial options. For what it's worth, for anyone wanting a large outdoor "catio," you can pretty easily modify large covered dog kennels to be cat-proof--you can add zip ties to the tarp roofs to close gaps, cut an opening in the cage wall to make window access, and so on. Not quite as much work as building something wholly from scratch! As a random example, here's a $280 dog kennel vs a $280 catio, both on amazon.
If you're lucky, you can sometimes find these kinds of kennels secondhand on marketplace and just modify them from there. To be properly predator-proof, if that's a concern in your area, a structure should be covered in 1/2 in welded wire hardware cloth, which can be attached with screws and washers, wire ties, or industrial zip ties. (My aviary proper is predator proof but the airlock section is currently not. ) Ideally, you also want to cover down into the ground to prevent digging in/out, if you're on the dirt. If you're not able to fully predator proof, then make sure that your cats have an escape route to get quickly back into the house.
There's tons of options and it mostly depends on what you have space and resources for, but if you can make it secure, a catio is a great option for extra enrichment.
