I don't think a 5 blade will work well. I never tried one though.
The 4 blade hydro was not hard to plane, but it did take a little finesse to keep the motor from over reving just as the boat comes over onto plane. At that point the hydro (w/o diffuser) will blow out a bit, but grabs gradually. Kinda like slipping the clutch on your car. Also lifted the arse end of the boat more, and made for a significantly better ride. If where you boat - it is rough (esp when planing) the Hydro is not for you.