Wheel Spacer Safe Size Range?

[KRAM36]

Seems I've read on here that spacers cause extra stress on the Axle Shaft?

I'm looking at possibly having to go with 20mm spacers according to this offset calculator.



I'm wanting to run 275/30R19 tires on 19x10.5 wheels with a 46 offset on the rear.

Is there a safe limit on the size of spacer used or all they all bad for the Axle Shaft?

Thanks!