Issue with SetHeight on GameMenuFrame

[Mayron]

Hi again

Quick-ish question..
I was wondering why a SetHeight method would not take affect on GameMenuFrame (where the Logout button is and others):

local menu = _G["GameMenuFrame"]
menu:SetHeight(menu:GetHeight() + 100)

I want to increase the size of that frame however it only works if I use it like the command below for example:

/run GameMenuFrame:SetHeight(340)

I thought maybe a blizzard function is blocking this but cannot find it. Also tried HookScript on the OnLoad handler but that did nothing so I'm out of ideas. Is this possible?

If you are wondering why I want to do this it is because I am trying to "skin" the GameMenuFrame using this:

local menu = _G["GameMenuFrame"]
menu:SetBackdrop(nil)
menu:SetBackdrop(Artwork_Import.ScaleBox)
menu:SetBackdropBorderColor(0,0,0,0.7)
menu:SetFrameStrata("TOOLTIP")
menu:SetFrameLevel("20")
menu:SetHeight(menu:GetHeight() + 100) -- Does not work

Thank you for reading