Menu Item Ordering and Z index

For some reason I can’t get my menu items to overlap the adjacent item. I am using an overlapping tabs menu and want the current menu item to show as forward… so you would think just raise the z-index for current_page_item, but even at z-index:9999999999999999999 it still will not move infront of the menu item to the left. The proper background image is displaying for the current menu item, just not in the right order. Any ideas? I thought it must be the menu structure, like overflow is hidden for lower menu items no matter what, or something.

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