Battling with CMSMenu styling again!

How do I set VERTICAL item spacing only? (ie, top and/or bottom spacing only)

Have a vertically aligned CMSMenu, items have a background colour, and I need to space them. If I modify CMSMenu1.MenuControl.ItemSpacing, it applies to all sides -- left and right as well as top and bottom. This then throws out the alignment with the left margin of the page.

In the styles I can add a border-bottom: solid 10px transparent to CMSMenuItem, but then the height of the last menu item is always reduced. If I also include border-bottom: solid 10px transparent in CMSMenu, then the height of the first and last menu items are increased!

Thanks,
Sharon.