A triple 47 Fountain and a single 271 are two very different boats, what works on the 47 might not work on the 271 at all. I would not compare the two.

x dim on a formula
 

I do a lot of x dim chandes and Formulas i would notch the bottom in about 10 inches.Raise the x so prop shaft is 4.5 inches below the vee and ru n a 4 blade Bravo 1.Remenber hatch clearance ,exhaust holes ,and the motor will have to be moved back as you go up ! Just talking from past projects we have done.

When you notch the bottom, how wide do you notch it? When you say 10", I assume you mean forward 10". How wide & how high is the notch? Anyone else with experience in notching transoms?