Squishing to horizon is not the same as disappearing bottom up behind it.

"Then you pull out you long distance lense and you can see the clouds that disappeared past the horizon"

Refraction over the horizon. You are seeing the clouds higher than they are hence you can see them.

This is the opposite of what you must demonstrate ... the disappearence of clouds bottom up without using curvature.

On a flat earth those clouds would just become infinitesimally small.

The reason you think objects will disappear behind the horizon, bottom up, is because that is what you see in real life ... on our spherical globe. Since you think the earth is flat, that is what you assume would happen on a flat eaeth. Any experiment would then be evidence of your assumption.

But again, perspective doesn't cause objects to disappear bottom up, it only causes squishing.

The concept of perspective is easily and completely demonstratable on paper. There's no disappearence of anything.