If I increase the font size for a TAdvOfficeFontSizeSelector, the drop down becomes unreadable since the font size of the drop down items is also increased but the line spacing is not.
I personally think it should follow the same behavior that you see for TAdvOfficeFontSelector where the drop down font size can be set separately using the FontSize property which is not available for the TAdvOfficeFontSizeSelector... and of course adjust the line spacing accordingly as it does for the TAdvOfficeFontSelector control.
Using TAdvOfficeFontSelector and TAdvOfficeFontSizeSelector version 1.2.7.0 in XE6.