1 If that "tank" is a tank is in the correct location to catch the over flow from the radiator. (much like my 1950 Plymouth inline six)
2 Note the seated gunner in the left side picture. His position indicates a seat on the right side of the gunner's cockpit. I recall (and I do not have it within reach) The Wellman or Model Airplane drawing/plan, had the seat on the side and the rear of the cockpit held four MG magazines. this would be a more logical layout...
3 The Model is beautiful. The wood is awesome.
4. If the gunner was standing on the varnished wood in his flight boots, there would be circular whitish scratch/wear marks on that floor. Like standing on wet pavement in muddy boots, and twisting around in circles.