Custom Resolution Utility (CRU)

[ManiacOfMadness]

Hello. This is my first time using CRU (thanks a lot for your work, ToastyX!) and I'm trying to create the following custom resolutions:

1920 x 1080 @ 59.940Hz (60/1.001)
1920 x 1080 @ 50.000Hz
1920 x 1080 @ 49.950Hz (50/1.001)
1920 x 1080 @ 48.000Hz
1920 x 1080 @ 47.952Hz (48/1.001)

As you've probably noticed, my goal is to have smooth playback through the most common frame rate standards.
To achieve this, I tried using a custom extension block in CRU and added those 5 resolutions + a 1920x1080@60Hz one, in case that was needed in the extension block (my knowledge here is limited).
For 60hz, 50hz and 48hz I used "Automatic - LCD Standard" timing and for the remaining three I went manual and used custom values taken from this site's own Pixel Clock calculator.

Unfortunately, I have problems with the 49.950hz not showing as an option in the available frame rates, and with the 47.952hz getting an "out of range" message on my monitor.
Is there anything I can try, or have I hit a hardware limitation?

I'm using an LG IPS monitor plugged with a DVI cable to a GTX 650 on Windows 7 x64.