Thanks for the heads up on the carpet, I'll definitely look into that.

So far the hollow spot without legs has not been a problem. Even if it sinks a bit, the amp is right under it so there is only about a quarter inch it can go down before it lands on the amp. I very rarely carry anything in the trunk so that's why I'm not too worried about it warping or anything hitting the sub.

Of course, if I do need to carry anything heavy, we'll see how it goes. Lol.