Yes, with UberMenu Lite v3 it is easier now to centralise a horizontal menu…
.boxed #MainNav .ubermenu-main.ubermenu-horizontal > ul.ubermenu-nav,
.full-width #MainNav .ubermenu-main.ubermenu-horizontal > ul.ubermenu-nav {
text-align: center
}
Go to Appearance > Theme Options > Custom CSS and add that CSS to your Custom CSS box, or add it to your custom stylesheet.