I believe the only way to accomplish this would be to edit the source for the ancestor menu and change the MenuStyle property from ContemporaryMenu! to TraditionalMenu! Here is an excerpt from an ancestor menu (I've added the spacing and the comments):
on m_master.create
m_master=this
call super::create
this.text = "m_master"
// Supported values are: contemporarymenu! and traditionalmenu!
// Note: This setting affects the look of the ENTIRE menu.
//
// This setting can only be specified in the base/ancestor menu object,
// and it cannot be set (as far as I know) in the Menu Painter.
this.menustyle = contemporarymenu!
this.menutextcolor = 134217735
this.menubackcolor = 16777215
this.menuhighlightcolor = 134217741
this.textsize = -10
this.weight = 400
Best regards, John