Custom Resolution Utility (CRU)

[Yokai]

Hello I'm a complete CRU noob, & and in desperate need of help!

My monitor is a Alienware AW2521H 360hz & and I'm trying to create a custom res of 1720x1080 @ 240hz.

1. First I open NVIDIA control panel turn on display scaling with no scaling mode selected.
2. I opened CRU and I copy the 240Hz detailed resolution from the extension blocks, then I delete all extension blocks.
3. I delete all detailed resolutions, add a new 1720x1080 resolution with the details I copied.
4. I add a standard resolution of 1920x1080 @ 60hz. Click OK.
5. I run Restart64.exe. My display is now running 1920x1080 @ 60hz.
6. I open display adapter properties, list all modes, then I select the custom resolution I added, click apply. The screen goes black for 10 seconds then comes back still on 1920x1080 @ 60hz.

What is going on here??

If I go to Windows display resolution it says my recommended is 1720x1080. I can change to this resolution on get black bars on either side but I'm still on 60hz. If I change to 240 Hertz in Window display settings I get a black screen & have to enter safe mode to fix.

Any help would be much appreciated?