the factory gas spring is 710 newtons (160 lb)
stabilus offers units that will fit the H2 that are 800, 900, 1000 newtons in the 10mm rods.
if you want to mount your tire onto the door
you can get a 16mm or 18mm rod.
companys that armor plate H2s use these rods
http://www.carpentryasanart.com