Hi Theon! Shadow's mom here. Shadow is a front right amputee...we had a lot of litterbox issues here. I rescued him after his surgery (my petsitter found him with a horribly broken-beyond-repair leg) so he was taken to a clinic and underwent amputation. I do not know his age. Anyway, we had been through a trial of at least 7 different size/shape boxes til we hit on one that seems to fill the bill. I ordered it from Amazon. It is (I believe) the Petmate 22040 Giant Litter Pan. I can't find my paperwork but the picture looks identical to what I have and I know it came from Amazon. Shadow is a big boy and he apparently needed plenty of room to turn around.  His issue in the box, however, was with either stepping in his very fresh pee clumps or actually peeing on his own back foot. He would use the box in my bedroom then hop on my bed tracking wet litter everywhere! I was washing my bedding 4-6 days a week! Since we switched to this big box (no lid!) I can count on one hand the number of wet footprints on my bed episodes. I am very relieved to have found it. I am not sure why your little guy is having issues. My Shadow does sometimes step in his poop but it is rare, I think he just loses his balance briefly. Shadow is my first tripawd so everything is new to me. Maybe the info in Jerry's post will help and Theon will grow out of it? I hope so! Like Mona, Shadow is an expert litter flinger. I actually awarded him the gold medal for flinging...my sister's cat Sam won silver. Lol. With all my previous cats I always had litter boxes with lids, which is what I bought Shadow. After failing with those I then went to just pans in various sizes.