I just had a look at a video on the Daily Terror website, which is from a tracker website.
It shows the liberty descending slightly as it approached the impact point - the Cessna was slightly climbing towards the point - then the Liberty basically sat on the Cessna. So definitely ads a bit of weight - in my unexperienced mind at least - to the earlier suggestion of a low vs high wing situation. Although what you can do about that I have no idea.