Hide too big or too small?

So I have two sets of hides that I bought. One is the exo terra reptile cave medium, the other is large.

He just barely fits in the medium. When I first put it in his cage, he actually stuck out a bit alongside the bottom edge. Hes packed down the bedding in there so he isn't sticking out anymore.

The large is much bigger. He would fit for sure, but I know they like small spaces, and I think it might be too big.

I guess I'm asking how do I know when small is too small?

BTW he is about 34 inches long.

I always shovel bedding out of their hides to keep the smaller hides in there.. As long as they won't get burned by the heating pad or whatever is being used. I personally don't leave a hide in to where the snake pushes the hide up to fit. I upgrade before that. But that's just me.

Use the smaller size until the snake "wears the hide like a hat" then upgrade to the larger ones. You can always put additional bedding or crumpled paper into the larger hides in order to make them feel secure.