Finally a new update!
I installed the valves to the tank.

And then fit the whole package in the trunk, seems to fit ok.

I painted the cups for the air bags...

And installed the rear bags to check everything is fine. I took the old spring out and just screwed the upper cup to the bolt on the frame.

Looks low enough.

Now I need to modify the exhaust to get more clearance :( One modification leads to an other, and summer is coming...