Help! holes in the bottom of the front trunk, not rust related! Options

[bradtho]

I've got my work light underneath on the left so you can see better. There's a matching set on the right side that aren't lit up. They are shaped like a figure 8 (upside down in this view) meaning that it looks like someone put a small hole in, then decided they needed it bigger and offset. all 4 holes have this same size/shape.

First thing, any clue what these were for? Looking underneath, it appears that something was attached underneath, but the cars are so low I can't imagine what was attached.

Second, what would you do to plug them? I'm trying to prepare for the return of the rain (this is a DD). I was planning on just using some conical rubber stoppers, but the oblong shape is going to make that a non-starter. I'm afraid any kind of tape will just hold water and be worse than nothing at all. Is nothing at all my best shot?

It would be a real shame to let rust get started, it's in such great shape now.