No problem, mode creation is all a bit confusing I find.
Some useful links for anyone else struggling with modes;
How X generates its modepool
How to ensure your system is picking the correct modes/refresh rate
Also, this snippet is quite important (xrandr 'lies' about available refresh rates)
Option "DynamicTwinView" "boolean"
Enable or disable support for dynamically configuring TwinView on this X screen. When DynamicTwinView is enabled (the default), the refresh rate of a mode (reported through XF86VidMode or XRandR) does not correctly report the refresh rate, but instead is a unique number such that each MetaMode has a different value. This is to guarantee that MetaModes can be uniquely identified by XRandR.
When DynamicTwinView is disabled, the refresh rate reported through XRandR will be accurate, but NV-CONTROL clients such as nvidia-settings will not be able to dynamically manipulate the X screen's MetaModes. TwinView can still be configured from the X config file when DynamicTwinView is disabled.
Default: DynamicTwinView is enabled.