I'm more than a little familiar with Rosebud's WW1 archives.. I did a couple-three hundred hours of research for painting skins for the aircraft used in the WW1 flight simulator, "Red Baron 3D"... I also used it for several static models of Fokker Dr ls and D Vlls too, and their dioramas.. It's a marvelous research site and indeed, all too easy to get "sucked into" lol...
Regarding the "Harry Tate"... I know that was a typo with the "F.E. 8" ID... An R.E. 8 ("'Harry Tate", see?) is what you meant, I know) at the top, that indeed is translucent.. But it's also unpainted, being covered in just the clear dope... The camouflage paint has yet to be added, as you pointed out with "arrival day", EB...
F.E. 8: http://www.aviastar.org/air/england/raf_fe-8.php
I don't want a "Photo War", lol.. Too much bandwidth, lol... The only thing I was trying to point out is that the eyes are decieving at times, so one has to look at all the little tells and study those... Then keep and discard whatever cancels out or supports the hypothosis...
Like the bottom R.E.8.. Given that I can find no evidence of a roundel shadow on the top wing (like the top photo), I'm assuming (ya, I know, I know) that the bottom is likely painted in a "sky" or light grey grey color rather than just being covered with the clear dope...
Also, IMO, the rib tapes are creating an illusion of translucency, combined with lighting effects, like a reflector of some sort (I'm not a photographer though) is being used, and given the reflection off the wheel cover (which also contrasts to good effect the grey rubber that was common back then on aircraft tires), and the appearance of an overcast sky (which is not all that uncommon in France either, during the late Spring/early Summer), with the Channel storms causing a lot of weather over the mainland, makes good photography difficult at times...
However, I'll conceed that it is possible as well, that the top wing of the lower Harry Tate is finished in clear dope only, since I do see SOME kind of shadow, I think... Likely the spars... Apparently, this aircraft is undergoing it's first camouflage paint job, but we don't know where, when, or who, since their unit markings and squadron badges have yet to be applied...
So.. What does all this mean? Simple.. Paint the ribs on either side of the rib tapes if'n ya wanna to show shadows or translucency... I'd use powdered charcoal and a 1-"0" red sable brush were I doing it...
I personally wouldn't spend much time on it, unless the underside is the main focus, and I'd decided to display it inverted as the result of a crash-landing, or nosed-over in a shell-crater in No Man's Land (HOWEVER: This would negate the see-though effect as well, since there's no light source under the aircraft), with perhaps one of Rosebud's "Unfortunate Aviators" still in the rear cockpit ...
Observers/gunners generally had a shorter life-expectancy than pilots (fighter pilots would want to aim well in order to incapacitate/kill the GIB as quickly as they could, for their own safety while finishing the attack), although with most recce flights, the Observer was the Mission Commander and an officer first, gunner second and didn't or couldn't spend a lot of time with their guns, at least not the amount that the bombers' dedicated Gunners did...
Think I just got a diorama idea!
This was the practice on both sides (and the first flying job Von Richthofen had as a "Flying Uhlan") However, MvR was different from most Observers in recce aircraft in the fact that he was an exceptional marksman...