I'd been using Catsan for a couple of months without any trouble. On the advice of her breeder, I bought her a larger tray and a couple of weeks later I started mixing new litter in with her Catsan (a paper-based pellet-type). She managed with the new litter mixed in for the first week, but after it had been in for a few days in the second week she started her balancing act. I figured that she was probably trying to tell me that the litter was getting too low for her, so I cleaned out the tray and re-filled it with the Catsan and Paper-litter mix. She managed with this again for a day or two and then started perching on the side again. This time I knew that the tray wasn't low (still loads of litter left) and it was still clean, so I assumed that she maybe didn't like the new paper-based litter that she was getting mixed in her tray. So when I cleaned and re-filled her tray after that accident I swapped the paper-based litter for wood-based litter (I'm trying to gradually get her off Catsan, as it's not always available in my local shop). Maybe I've changed too many things for her in too short a time, though??

That's one of the things I'm worried about. She has had loose poo a couple of times the last couple of weeks, but I can't recall if any of these times have been during her balancing acts. I'll definitely watch out for that in case she's having trouble going properly. Thanks for mentioning it.

Strangely, my kitten has always placed her front paws on the side of the litter tray when she goes for a poo; it's only recently that she's decided to place one of her back legs on the side, too (when she goes for a wee she just sits straight inside the tray on top of the litter). The litter tray she now uses is one of the biggest ones I know of, but you may be right about trying out a hooded one if all else fails...

My cat is an indoor cat; only going outside on a harness to walk and play, so I can't let her do her business outside.

Thanks for all the help, guys!