If you have the 'G-Sensor Precision' set to the lowest value of '2G' then just a lesser more gentle impact is required to trigger the 'locking' of the files ... Likewise if you have the 'G-Sensor Precision' set to the highest value of '5G' then a much more forceful impact is necessary before any files get 'locked' i.e. Write-Protected
However practically speaking how these 'G' values translate onto the Road I think you'll have to experiment a bit and see what best works for you
At the end of the day though, no matter what the G-factor is set at, you won't be missing any evidence of any impact because you're more than likely going to examine (and copy) the relevant files as soon as you get home anyway aren't you ? I know I would ! The only difference is going to be whether or not the relevant files were 'locked' during the impact ... make sense ?
Unfortunately if your vehicle is hit whilst it's parked up the Mini 0801 does not currently have any way of recording what happens immediately after the impact. Perhaps something for the Manufacturers to consider for future versions ...