Stretch tuning needed for marimba?

[Bence Varga]

I am building my own marimba and I read about an advice that over C#6 bars should be tuned +1 cent per bar. In a way that C#6 +1, D6 +2, D#6 +3 cent. Is this really needed, or not? Does anyone have experience about this?

[Clay Schaeffer]

With pianos the higher notes are tuned slightly sharp to match the upper partials of the lower notes which go sharp because of string stiffness. I don't know if this applies to marimba bars but it may.

Side note - the reason grand pianos and spinets can't play in tune with each other is because the sharping of the longer thinner less stiff strings of the grand piano is less pronounced than that of the short fat stiffer strings of the spinet.