Been playing about with mine during the day, seeing if different positioning on the bumpers etc made any difference.
What I noticed was that if the tailgate remained closed for an hour or so, it always struggled to open the first time. After that, it opens everytime, no
problem. It's almost as if the strut, having been compressed for an hour, has difficulty reaching maximum force. Once it's been extended once, the tailgate opens fully time after time.
Even when it doesn't fully open, it still opens a couple of inches, only needs a touch with one finger to
help it on it's way. Still a lot better than the OEM struts.