I agree with Catch22. The entire cover panel was nothing more but an aerodynamic fairing. Being a set for a field modification couldn't be any reinforcing fuealge panel just because of its attaching. Although the RB camera wasn't so long it had the long leans of focal length 50 cm and the antiglare tube that protruded a little bit at the bottom. For the reason the fairing with the moisture/water deflector also could protect the camer lens against the oil droplets from the engine exhaust or the cooling system of the engine compartment coming out at the bottom.
Regarding the extend fuel drain tube .. it should be kept in mind that the main and also the belly jettisoned fule tanks were attached quite close to the camera compartment... Actuallly the pilot was sitting on the main tank. Contrary to that the oil tank(s) were installed at the front of the engine compartment and didn't go through the firewall in front of the cockpit too much. So getting the oil at the back this way wasn't rather possible rather. But the fuel filler and pipes were just going close to there and the possibility of appearing the fuel leaks there was highly likely. For the reason the draining extended tube seems to be quite logical reason for using it when the rΓΌstsatz R2 was installed in order to protect the camara mount and lens against the fuel as well. But I don't think it was any standard way of draining as the drain was already installed there but a little bit back between the bulkheads 3 and 4 also seen in the B&W shot from the manual.
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