Oh well, puke is a whole different story altogether and has zero to do with the litterbox (or for that matter, defiance) youre anthropomorphizing.
Think of cats puking as quite similar to toddlers up chucking. It comes on suddenly and catches them totally by surprise so they do what comes naturally. No harm no foul. The only reason kids dont generally do that past toddler age is a combination of verbal skills and realizing how much of a mess it will be (oh yeah, the knowledge of how handy toilets are helps immensely. Human kids develop that knowledge; unfortunately cats dont :). You were relating it to fears of litterbox accidents so I naturally assumed poop.
So then Milo’s good bathrooming record is unblemished, basically.?
If you’re asking me how high you should put it, I would say as high as you need it to be to take the physical strain off of you. He’ll adjust. Most cats can leap up to the top of the refrigerator with no problem so around waist high for you isn’t even a hiccup for him (unless he’s an old cat with arthritis) but he looks pretty spry in the photos I’ve seen.
For crying out loud, he hops up to the top of the bannister railing perching precariously just to enjoy the wintertime view. I hardly think hopping up 2–4 feet onto a sturdy pallet is any problem at all.
But if you wanted to make it a little fun for him then put up a few graduated sturdy dshelves on the wall or a few graduated height wooden boxes so its like a little stairway. He’ll love it. Like his own custom playground.
But if youre still nervous, Leave a little treat out for him the first few times and that will do the trick for sure.
Cars are climbers by nature and doing a little climbing or jumping to get to the litterbox is a fun activity. We with our aging knees wouldn’t appreciate it but Milo will most likely love it.
So, put it as high as you need it for you. He will adapt.
And in the highly unlikely event that he doesn’t initially, just put it back on the floor and do it in smaller incremental steps each separated by a week or so. But I hardly think that will be needed.