[Christ]

Sure, it's better than nothing, but it's not going to help as much as a full front belly pan, and those holes are going to kill some gains, especially the front one... you can probably already imagine the parachute effect that one particularly will have, since part of it is cut through an angle.

Looking at the first pic, it would be pretty simple to just get a sheet of ABS plastic and trim it to fit the mounting holes in the bottom of the bumper cover, then trim it back to fit into the cross-member and between any moving parts on either side.

If you really wanted to get fancy, you could make some spats on the front belly pan at each side that would keep the air from flowing through the suspension components that can't normally be covered, due to movement.