UberMenu includes a built-in grid system that can be used to layout your submenus.
The width of the column depends on the width of the contents.
By applying a 5-column grid to the submenu, each item becomes 20% of the submenu's width. Note that the submenu must have a defined width (be full-width or have an explicit width) for this to work.
The contents of long items are forced to wrap
Setting the default column width to 1/3 would result in this layout: