One main issue.
Firstly the gas dampers are much better than the rubbish that suplex supply. Good luck with the Suplex!
HOWEVER, the main issue is adequately reinforcing the rear top mounts. The original set up put very little load through this top mount as the original dampers act in only one direction. So the top mount is single layer sheet metal. i.e. A hole through the inner wing.
The problem being that the stress and load through a double acting damper is much greater than the original mount is capable of taking. The hydragas units took all of the compression forces so the original dampers were just there to control the rebound.
I have a SUPLEX/ gaz damper setup and despite reinforcing the rear top mounts they have cracked twice and had to be repaired.
Reinforcing the mounts just moved the stress points and so the inner wing cracks in different places! I currently have another crack in the nearside mount area!