We have many bed sizes here, and after getting an inclinometer find some interesting issues. With a 6 inch...I.e. 5 inch indent...I got 3 different angles on 3 different beds...3.5 deg, 4.5 deg, and 4.6 degrees. If I remember correctly passing 5 inches starts giving the full benefit...6 inches is to make sure. A UK bed means that's around 4.5 degrees. 5 degrees to make sure. Looks like I need to get the larger bed risers then. Any comments on this are welcome. Of course there are benefits from even 3 inches, especially with traction....but one Ned's to feel the real effect.