Underground belt can be placed directly on normal belt. Additionally, placing an underground belt will remove any normal belts facing the same direction between the end points (as in Quick UG).
A bit of an issue is that placing an underground belt with this mod may also remove belts that are wanted.
Especially when placing a blueprint which has belts on top of underground belts. If the belts are placed first and the undergound belt is finished afterwards, it will remove the belts that used to be on top.
I'm not sure what you mean by "blueprint which has belts on top of other belts". If you are placing blueprints on top of existing belts then I should think you need the normal belts to be replaced with underground belts. And no blueprint can have two belts in one spot as far as I'm aware, so I don't understand the problem.
