Variable group widths in single-column dashboard panels (using CSS?)

Hey Splunk community!

I currently have a dashboard with a number of panels, and each panel has 5 groups:

panel 1: | grp1 | grp2 | grp3 | grp4 | grp5 |

panel 2: | grp1 | grp2 | grp3 | grp4 | grp5 |

panel 3: | grp1 | grp2 | grp3 | grp4 | grp5 |

etc.

I've chosen to use 1 column per panel so I can get more than 3 elements in a row, and so I can have a custom html title at the top, like this:

    module name="StaticContentSample" layoutPanel="panel_row4_col1" 
    module name="HiddenSavedSearch" layoutPanel="panel_row4_col1_grp1" autoRun="True"
    module name="HiddenSavedSearch" layoutPanel="panel_row4_col1_grp2" autoRun="True"
    module name="HiddenSavedSearch" layoutPanel="panel_row4_col1_grp3" autoRun="True"
    module name="HiddenSavedSearch" layoutPanel="panel_row4_col1_grp4" autoRun="True"
    module name="HiddenSavedSearch" layoutPanel="panel_row4_col1_grp5" autoRun="True"

Currently, each of these groups is the same width (20% because there are 5). However, I'd like to customize the group widths so grps 1, 3, and 5 are each 10%, and grps 2 and 4 are 35%.

FWIW, the groups I'd like to be 35% each contain 1 flashchart, while the 10% groups contain a set of single-value metrics. (Not sure if that's relevant, though.)

Any suggestions on how to make this custom-width modification via CSS or otherwise?

Thanks! Seth