The buffer is integral to the chassis/armor but the endcaps are not the hardox sides, but welded in caps.
The buffertank was pressuretested before and after the welding to the chassis/armor.

I contemplated using the armor as pressure stressed, but refrained from it as any battledamage to the armor would compromise the safety.
In the end, the welded in end caps add "only" 300 grams.