Admin overlay covers TAB content

In 7.26 using the Seven admin theme overlay, the grey shortcut menu masks the tabs on - for example - People (see screenshot)

It's possible (but not necessarily intuitive) to click off the grey shortcut menu, but I prefer to add a 75px margin to drop the page content below the problem area. Since this involves the sin of hacking core, I would much rather see it fixed centrally in 7.27, even though it's a pretty minor matter.

File extract from: site_root//modules/overlay/overlay-child.css (~ lines 17-27)

#overlay {
display: table;
margin: 0 auto; /* a change to 75px [replacing 0 as the first item after the colon] clears the overlay menu */
min-height: 100px;
min-width: 700px;
position: relative;
padding: .2em;
padding-bottom: 2em;
padding-right: 26px; /* LTR */
width: 88%;
}

This is happening on Chrome Version 32.0.1700.102 & Firefox 27.0 on Ubuntu 13.10 - but colleagues have also demonstrated it using Chrome on Windows 8

The main theme in use on the site is Bootstrap 3

Thanks, Stonezafu