Why place the Cardboard pieces underneath the Virtual Walls?

[IndyGuy]

I bought a Roombud for my Roomba, and when I received it, it came with two small cardboard pieces that instructed the user to place them underneath the VWs, as the Roombud increases the Roomba tendency to escape (which it does, even if you take care to make sure the sensors are not covered by the Roombud). This makes little sense to me. The Roomba height is not affected by the Roombud cover, so why are the cardboard pieces needed?

[Mooba]

Remember that the IR signal beam from the virtual wall is cone shaped and not flat. By raising the virtual wall, the IR "cone" can look over the small amount of the RoomBud cover that might pop up and block the signal if the virtual wall is just placed on the floor. You may also find that the Roomba escapes when the virtual wall is a bit lower in general than the Roomba.

The picture here is taken with an IR camera showing the shape of the virtual wall signal.

[dsscheibe]

You may also find that the Roomba escapes when the virtual wall is a bit lower in general than the Roomba.

That might explain why my Roomba without a roombud got past the virtual wall into the kitchen Yesterday. The linolium is about 1/3" shorter than the carpet.