I have done this mod on my Bav 46. Added a single gas strut to the forward end of the seat. It is rated at 200kg. I simple got a mobile car gas strut repairer around. He was able to pressurise the strut to the required amount. It took 2 or 3 times to get it right. The problem is that the strut lifts one side on the seat only. It would have been better to buy two struts, one at each end then the seat would lift evenly.