WoWInterface - Small help with AceGUI layout

I am trying to follow a simple example posted by the AceGUI author. I think I am missing something simple.
Ultimately I am trying to have an independent frame that contains large textbox that scales to size.

Code:

function CreateScrollFrame(widget, height)

    local scrollcontainer = AceGUI:Create("SimpleGroup") -- "InlineGroup" is also good

    scrollcontainer:SetFullWidth(true)

    if height then

        scrollcontainer:SetHeight(height)

    else

        scrollcontainer:SetFullHeight(true)

    end

    scrollcontainer:SetLayout("Fill")



    widget:AddChild(scrollcontainer)



    local scrollFrame = AceGUI:Create("ScrollFrame")

    scrollFrame:SetLayout("Flow")

    scrollcontainer:AddChild(scrollFrame)



    return scrollFrame

end



initImportGui = function ()

    local frame = AceGUI:Create("Frame")

    frame:SetWidth(500)

    frame:SetHeight(600)

    frame:SetTitle("Import/Export List")



    local scrollFrame = CreateScrollFrame(frame)

    

    local editBox = AceGUI:Create("MultiLineEditBox")

    editBox:DisableButton(true)

    editBox:SetLabel("")

    editBox:SetFullWidth(true)



    scrollFrame:AddChild(editBox)

    editBox:SetFullHeight(true)



    return frame

end

I commented out the actual editbox and the frame defined as "SimpleGroup" that has "SetFullHeight(true)" does not scale to the height of the containing frame. Any idea what I'm missing?