If your existing prop allowed you to reach max rpm at WOT then dropping dia 1" and add 1" of pitch shouldn't make a huge difference. But... Rule of thumb says you add 1 1/2 - 2" of pitch. So it might be a couple of hundred rpm off.
Just make it clear to prop shop that final acceptance is subject to sea trial and if you can't reach max rpm or max speed then they will repitch it.
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