I went into Window/Model Info/Dimensions and do not see where I can modify the numbers. (Using a line from Indiana Jones) I must be "digging in the wrong place"(?). I did find that under Entity Info when the dimension object is selected you can 'Align to Dimension' and then position the text "Above" but, this could get ugly at odd angles of view.
I like your way better, I'm just missing something or need a little more specific directions (no big surprise here).