Markets should remain flat till the meeting since it looks like a 0.50% cut is factored in already.
If the cut is 0.25%, the markets will fall a bit
If there is no cut, the markets will crash. I will buy since it means the Fed doesnt think there would be a bad recession.
If the cut is 0.50%, markets would rally a little and I would use that opportunity sell 25% of my portfolio.
If the cut is a whopping 0.75%, markets will probably zoom and I will dump stocks (40% or more) because it would be a real bearish sign for the Fed to cut so deep.
Note - where this can go wrong is if the Fed behaves irrationally and cuts rates again to appease the markets. We would sell thinking a bad recession is on the way, but reality may be otherwise.