Those of you with a comprehensive collection of Double Gun Journals should revisit Vol.14 Issue 4 (Winter 2003) for a reminder of Ernst Steigleder's verschluss with three extensions!
(One on each side as pictured above, and one as a rib extension between the chambers, all cross-bolted!)
Sounds clumsy, but due to the skill of the maker it still manages to look elegant in a Teutonic sort of way....