Karl-Fritz Schröder, Bordfunker with Erprobungsgruppe 210; Schnellkampfgeschwader 210 and Zerstörergeschwader 1 told me that the support belt was fastened to either side of the cockpit interior with a large, strengthened centre section. In combat, their role was a nightmare, he said. If the pilot needed to have a 20 mm. ammo drum replaced, the Bordfunker had to do it, almost certainly while the pilot was throwing their Bf 110 around in the sky. So, while that was going on, they had to remove the old drum, remove a new drum from its secure fitting, and fit it onto the 20 mm. cannon. The same for their own rear firing MG. Thye would be defending the rear of the aircraft and themselves, run out of ammo, so then remove the old drum and try to fit the new one while the attacker was quite happily firing away at the rear of the 110 without any return fire coming at them.
