Monitor LG 29UM58-P overclock to 75Hz

[xpertvision]

i cant overclock my monitor LG 29UM58-P from 60Hz to 75Hz in MacOS

but in windows using the nvidia drivers i can do the overclock and works fine:
 

when i try to do the same in MacOS using the same settings in SwitchResX the screen gets black and starts to flick
this is my settings using SwitchResX on MacOS:
 
any ideas why this append? as you can see in the screenshots the settings are the same both in Windows and MacOS... but doenst work in MacOS i am doing something wrong? maybe i need to edit something is MacOS?

Edited April 12, 2018 by xpertvision