Alec,
On this and other threads you have asked for comments, good and bad, and at times have complained that you have not gotten any response. In this thread then Alexandre replies with comments on how to improve your work in general and more specifically he mentions possibly reworking the groundwork. Your response to his comments is to say that your groundwork is "spot on", thereby implying that Alexandre's opinion is wrong. I would suggest that this is not the best way to encourage people to help and offer comments. Please don't take this the wrong way, I am bringing this up to try and help, and maybe reduce some of your frustration.
As for my thoughts about this segment, I do like the activity of it, there is a lot going on, and the chaos of trench fighting is captured well. I especially like the use of the airplane(Sopwith Camel?). The airplane might be more effective, though, if you mounted it on something less obtrusive, I have seen clear styrene rods in the LHS, maybe something like that, if it had the strength to hold it up, would be less noticeable. Another thing to think about is scale, in 1/72 barb wire would be very thin wire and the barbs would be practically invisible. Curious about what might work to represent this I made this:
All I did was take very thing copper wire, 1 strand from some old speaker cable, and make successive loops over another piece of wire. Each small loop was then pulled out to form a crink in the wire and the whole wire was wrapped around a dowel. It wasn't hard to do, and it might make a big difference to the overall impression of this or future dios.
Finally, I just want to second something Alexandre said, slow down! Take your time, it isn't a race.
Matt