I've yet to see "as far as we should" if the earth was flat.
I can't reproduce what is claimed in the Bishop Antecdote even at half the distance. And yet you, Tom, say you did it often; anytime you had your doubts.
Every level alignment observation I've made suggests a convex surface. As impressive as a 17-mile mirror flash was, it's still not proving flat. I've done a 800' to 400' mirror test through thick haze over a 20 mile span with a small 3"×5" mirror. But the surface level record, on a clear day, with a 12"x48" mirror is only 17.5 miles. Is that "farther than it should" on a 3959 mile radius globe with an atmosphere? Maybe. But there are ways it could happen. Or maybe the globe is larger and the convexity less.
Do the mirror test across Monterey Bay from Santa Cruz. If you can play the "shouldn't be able to see" game then I'll play the "should be able to see" counter game. If there are atmospheric reasons why you can't see forever on a flat earth, there are atmospheric reasons why we can, sometimes, see farther than on a globe with no atmosphere.