TRUE 120: How much tension on mounting screws?

Hi. I've got a new Thermalright Ultra Extreme 120 BE. This is my first experience with spring loaded CPU cooler mounting screws. I am used to the clip on AM2 style mounting a la Zalman 9700, etc. Can anyone tell me definitively if I am supposed to tighten the screws all the way down, until they are fully seated and tight or just until the CPU cooler is snug and does not slide around easily? On first mount I tightened them down fully and noticed that the backing plate was slightly warped with the tension from the screws so I backed them off. I want to make sure I am getting the full cooling benefit of the cooler, any info would be appreciated. ---Chikn