Hi Andy,
While it's possible to resize the 120px width of the flyout-menu, I don't recommend it as it will reduce the available space in the main-copy section to less than 620px for things like the dashboard (in the 800px narrow view).
How about using width=/height= on the image statements for your affiliates to reduce their display to 120px wide instead? If you do it proportionally, the display will look natural and you won't have a tricky fiddling job with the CSS to do.