I have a 1" steel shaft in my FX for a jackshaft. Running 1" pillow block bearings and had the ends turn down to 3/4". Never had a problem in 3 years.
Running a 28 briggs OHV that isn't...........well Stock!
I wouldn't use anything exotic that way if you ever do have problems parts are easy to obtain. But you won't.
And I only run 2 bearings, no need for a 3rd.
Paul